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TA16-250A: The Increasing Threat to Network Infra... US-CERT
Original release date: September 06, 2016 | Last revised: September 20, 2016

Systems Affected

Network Infrastructure Devices
 

Overview

The advancing capabilities of organized hacker groups and cyber adversaries create an increasing global threat to information systems. The rising threat levels place more demands on security personnel and network administrators to protect information systems. Protecting the network infrastructure is critical to preserve the confidentiality, integrity, and availability of communication and services across an enterprise.

To address threats to network infrastructure devices, this Alert provides information on recent vectors of attack that advanced persistent threat (APT) actors are targeting, along with prevention and mitigation recommendations.
 

Description

Network infrastructure consists of interconnected devices designed to transport communications needed for data, applications, services, and multi-media. Routers and firewalls are the focus of this alert; however, many other devices exist in the network, such as switches, load-balancers, intrusion detection systems, etc. Perimeter devices, such as firewalls and intrusion detection systems, have been the traditional technologies used to secure the network, but as threats change, so must security strategies. Organizations can no longer rely on perimeter devices to protect the network from cyber intrusions; organizations must also be able to contain the impact/losses within the internal network and infrastructure.

For several years now, vulnerable network devices have been the attack-vector of choice and one of the most effective techniques for sophisticated hackers and advanced threat actors. In this environment, there has never been a greater need to improve network infrastructure security. Unlike hosts that receive significant administrative security attention and for which security tools such as anti-malware exist, network devices are often working in the background with little oversight—until network connectivity is broken or diminished. Malicious cyber actors take advantage of this fact and often target network devices. Once on the device, they can remain there undetected for long periods. After an incident, where administrators and security professionals perform forensic analysis and recover control, a malicious cyber actor with persistent access on network devices can reattack the recently cleaned hosts. For this reason, administrators need to ensure proper configuration and control of network devices.

Proliferation of Threats to Information Systems

SYNful Knock

In September 2015, an attack known as SYNful Knock was disclosed. SYNful Knock silently changes a router’s operating system image, thus allowing attackers to gain a foothold on a victim’s network. The malware can be customized and updated once embedded. When the modified malicious image is uploaded, it provides a backdoor into the victim’s network. Using a crafted TCP SYN packet, a communication channel is established between the compromised device and the malicious command and control (C2) server. The impact of this infection to a network or device is severe and most likely indicates that there may be additional backdoors or compromised devices on the network. This foothold gives an attacker the ability to maneuver and infect other hosts and access sensitive data.

The initial infection vector does not leverage a zero-day vulnerability. Attackers either use the default credentials to log into the device or obtain weak credentials from other insecure devices or communications. The implant resides within a modified IOS image and, when loaded, maintains its persistence in the environment, even after a system reboot. Any further modules loaded by the attacker will only exist in the router’s volatile memory and will not be available for use after the device reboots. However, these devices are rarely or never rebooted.

To prevent the size of the image from changing, the malware overwrites several legitimate IOS functions with its own executable code. The attacker examines the functionality of the router and determines functions that can be overwritten without causing issues on the router. Thus, the overwritten functions will vary upon deployment.

The attacker can utilize the secret backdoor password in three different authentication scenarios. In these scenarios the implant first checks to see if the user input is the backdoor password. If so, access is granted. Otherwise, the implanted code will forward the credentials for normal verification of potentially valid credentials. This generally raises the least amount of suspicion. Cisco has provided an alert on this attack vector. For more information, see the Cisco SYNful Knock Security Advisory.

Other attacks against network infrastructure devices have also been reported, including more complicated persistent malware that silently changes the firmware on the device that is used to load the operating system so that the malware can inject code into the running operating system. For more information, please see Cisco's description of the evolution of attacks on Cisco IOS devices.

Cisco Adaptive Security Appliance (ASA)

A Cisco ASA device is a network device that provides firewall and Virtual Private Network (VPN) functionality. These devices are often deployed at the edge of a network to protect a site’s network infrastructure, and to give remote users access to protected local resources.

In June 2016, NCCIC received several reports of compromised Cisco ASA devices that were modified in an unauthorized way. The ASA devices directed users to a location where malicious actors tried to socially engineer the users into divulging their credentials.

It is suspected that malicious actors leveraged CVE-2014-3393 to inject malicious code into the affected devices. The malicious actor would then be able to modify the contents of the Random Access Memory Filing System (RAMFS) cache file system and inject the malicious code into the appliance’s configuration. Refer to the Cisco Security Advisory Multiple Vulnerabilities in Cisco ASA Software for more information and for remediation details.

In August 2016, a group known as “Shadow Brokers” publicly released a large number of files, including exploitation tools for both old and newly exposed vulnerabilities. Cisco ASA devices were found to be vulnerable to the released exploit code. In response, Cisco released an update to address a newly disclosed Cisco ASA Simple Network Management Protocol (SNMP) remote code execution vulnerability (CVE-2016-6366). In addition, one exploit tool targeted a previously patched Cisco vulnerability (CVE-2016-6367). Although Cisco provided patches to fix this Cisco ASA command-line interface (CLI) remote code execution vulnerability in 2011, devices that remain unpatched are still vulnerable to the described attack. Attackers may target vulnerabilities for months or even years after patches become available.

Impact

If the network infrastructure is compromised, malicious hackers or adversaries can gain full control of the network infrastructure enabling further compromise of other types of devices and data and allowing traffic to be redirected, changed, or denied. Possibilities of manipulation include denial-of-service, data theft, or unauthorized changes to the data.

Intruders with infrastructure privilege and access can impede productivity and severely hinder re-establishing network connectivity. Even if other compromised devices are detected, tracking back to a compromised infrastructure device is often difficult.

Malicious actors with persistent access to network devices can reattack and move laterally after they have been ejected from previously exploited hosts.
 

Solution

1.    Segregate Networks and Functions

Proper network segmentation is a very effective security mechanism to prevent an intruder from propagating exploits or laterally moving around an internal network. On a poorly segmented network, intruders are able to extend their impact to control critical devices or gain access to sensitive data and intellectual property. Security architects must consider the overall infrastructure layout, segmentation, and segregation. Segregation separates network segments based on role and functionality. A securely segregated network can contain malicious occurrences, reducing the impact from intruders, in the event that they have gained a foothold somewhere inside the network.

Physical Separation of Sensitive Information

Local Area Network (LAN) segments are separated by traditional network devices such as routers. Routers are placed between networks to create boundaries, increase the number of broadcast domains, and effectively filter users’ broadcast traffic. These boundaries can be used to contain security breaches by restricting traffic to separate segments and can even shut down segments of the network during an intrusion, restricting adversary access.

Recommendations:
  • Implement Principles of Least Privilege and need-to-know when designing network segments.
  • Separate sensitive information and security requirements into network segments.
  • Apply security recommendations and secure configurations to all network segments and network layers.
Virtual Separation of Sensitive Information        

As technologies change, new strategies are developed to improve IT efficiencies and network security controls. Virtual separation is the logical isolation of networks on the same physical network. The same physical segmentation design principles apply to virtual segmentation but no additional hardware is required. Existing technologies can be used to prevent an intruder from breaching other internal network segments.

Recommendations:
  • Use Private Virtual LANs to isolate a user from the rest of the broadcast domains.
  • Use Virtual Routing and Forwarding (VRF) technology to segment network traffic over multiple routing tables simultaneously on a single router.
  • Use VPNs to securely extend a host/network by tunneling through public or private networks.


2.    Limit Unnecessary Lateral Communications

Allowing unfiltered workstation-to-workstation communications (as well as other peer-to-peer communications) creates serious vulnerabilities, and can allow a network intruder to easily spread to multiple systems. An intruder can establish an effective “beach head” within the network, and then spread to create backdoors into the network to maintain persistence and make it difficult for defenders to contain and eradicate.

Recommendations:
  • Restrict communications using host-based firewall rules to deny the flow of packets from other hosts in the network. The firewall rules can be created to filter on a host device, user, program, or IP address to limit access from services and systems.
  • Implement a VLAN Access Control List (VACL), a filter that controls access to/from VLANs. VACL filters should be created to deny packets the ability to flow to other VLANs.
  • Logically segregate the network using physical or virtual separation allowing network administrators to isolate critical devices onto network segments.
     

3.    Harden Network Devices

A fundamental way to enhance network infrastructure security is to safeguard networking devices with secure configurations. Government agencies, organizations, and vendors supply a wide range of resources to administrators on how to harden network devices. These resources include benchmarks and best practices. These recommendations should be implemented in conjunction with laws, regulations, site security policies, standards, and industry best practices. These guides provide a baseline security configuration for the enterprise that protects the integrity of network infrastructure devices. This guidance supplements the network security best practices supplied by vendors.

Recommendations:
  • Disable unencrypted remote admin protocols used to manage network infrastructure (e.g., Telnet, FTP).
  • Disable unnecessary services (e.g. discovery protocols, source routing, HTTP, SNMP, BOOTP).
  • Use SNMPv3 (or subsequent version) but do not use SNMP community strings.
  • Secure access to the console, auxiliary, and VTY lines.
  • Implement robust password policies and use the strongest password encryption available.
  • Protect router/switch by controlling access lists for remote administration.
  • Restrict physical access to routers/switches.
  • Backup configurations and store offline. Use the latest version of the network device operating system and update with all patches.
  • Periodically test security configurations against security requirements.
  • Protect configuration files with encryption and/or access controls when sending them electronically and when they are stored and backed up.
     

4.    Secure Access to Infrastructure Devices

Administrative privileges on infrastructure devices allow access to resources that are normally unavailable to most users and permit the execution of actions that would otherwise be restricted. When administrator privileges are improperly authorized, granted widely, and/or not closely audited, intruders can exploit them. These compromised privileges can enable adversaries to traverse a network, expanding access and potentially allowing full control of the infrastructure backbone. Unauthorized infrastructure access can be mitigated by properly implementing secure access policies and procedures.

Recommendations:
  • Implement Multi-Factor Authentication – Authentication is a process to validate a user’s identity. Weak authentication processes are commonly exploited by attackers. Multi-factor authentication uses at least two identity components to authenticate a user’s identity. Identity components include something the user knows (e.g., password); an object the user has possession of (e.g., token); and a trait unique to the specific person (e.g., biometric).
  • Manage Privileged Access – Use an authorization server to store access information for network device management. This type of server will enable network administrators to assign different privilege levels to users based on the principle of least privilege. When a user tries to execute an unauthorized command, it will be rejected. To increase the strength and robustness of user authentication, implement a hard token authentication server in addition to the AAA server, if possible. Multi-factor authentication increases the difficulty for intruders to steal and reuse credentials to gain access to network devices.
  • Manage Administrative Credentials – Although multi-factor authentication is highly recommended and a best practice, systems that cannot meet this requirement can at least improve their security level by changing default passwords and enforcing complex password policies. Network accounts must contain complex passwords of at least 14 characters from multiple character domains including lowercase, uppercase, numbers, and special characters. Enforce password expiration and reuse policies. If passwords are stored for emergency access, keep these in a protected off-network location, such as a safe.
     

5.    Perform Out-of-Band Management

Out-of-Band (OoB) management uses alternate communication paths to remotely manage network infrastructure devices. These dedicated paths can vary in configuration to include anything from virtual tunneling to physical separation. Using OoB access to manage the network infrastructure will strengthen security by limiting access and separating user traffic from network management traffic. OoB management provides security monitoring and can implement corrective actions without allowing the adversary who may have already compromised a portion of the network to observe these changes.

OoB management can be implemented physically or virtually, or through a hybrid of the two. Building additional physical network infrastructure is the most secure option for the network managers, although it can be very expensive to implement and maintain. Virtual implementation is less costly, but still requires significant configuration changes and administration. In some situations, such as access to remote locations, virtual encrypted tunnels may be the only viable option.

Recommendations:
  • Segregate standard network traffic from management traffic.
  • Enforce that management traffic on devices only comes from the OoB.
  • Apply encryption to all management channels.
  • Encrypt all remote access to infrastructure devices such as terminal or dial-in servers.
  • Manage all administrative functions from a dedicated host (fully patched) over a secure channel, preferably on the OoB.
  • Harden network management devices by testing patches, turning off unnecessary services on routers and switches, and enforcing strong password policies. Monitor the network and review logs Implement access controls that only permit required administrative or management services (SNMP, NTP SSH, FTP, TFTP).
     

6.    Validate Integrity of Hardware and Software

Products purchased through unauthorized channels are often known as “counterfeit,” “secondary,” or “grey market” devices. There have been numerous reports in the press regarding grey market hardware and software being introduced into the marketplace. Grey market products have not been thoroughly tested to meet quality standards and can introduce risks to the network. Lack of awareness or validation of the legitimacy of hardware and software presents a serious risk to users’ information and the overall integrity of the network environment. Products purchased from the secondary market run the risk of having the supply chain breached, which can result in the introduction of counterfeit, stolen, or second-hand devices. This could affect network performance and compromise the confidentiality, integrity, or availability of network assets. Furthermore, breaches in the supply chain provide an opportunity for malicious software or hardware to be installed on the equipment. In addition, unauthorized or malicious software can be loaded onto a device after it is in operational use, so integrity checking of software should be done on a regular basis.

Recommendations:
  • Maintain strict control of the supply chain; purchase only from authorized resellers.
  • Require resellers to implement a supply chain integrity check to validate hardware and software authenticity.
  • Inspect the device for signs of tampering.
  • Validate serial numbers from multiple sources.
  • Download software, updates, patches, and upgrades from validated sources.
  • Perform hash verification and compare values against the vendor’s database to detect unauthorized modification to the firmware.
  • Monitor and log devices, verifying network configurations of devices on a regular schedule.
  • Train network owners, administrators, and procurement personnel to increase awareness of grey market devices.

 

Shadow Broker Exploits
VendorCVEExploit NameVulnerability
FortinetCVE-2016-6909   EGREGIOUSBLUNDERAuthentication cookie overflow
WatchGuard   CVE-2016-7089ESCALATEPLOWMANCommand line injection via ipconfig
CiscoCVE-2016-6366EXTRABACONSNMP remote code execution
CiscoCVE-2016-6367EPICBANANACommand line injection remote code execution
CiscoCVE-2016-6415BENIGNCERTAIN/PIXPOCKET   Information/memory leak
TOPSECN/AELIGIBLEBACHELORAttack vector unknown, but has an XML-like payload
beginning with <?tos length="001e.%8.8x"?
TOPSECN/AELIGIBLEBOMBSHELLHTTP cookie command injection
TOPSECN/AELIGIBLECANDIDATEHTTP cookie command injection
TOPSECN/AELIGIBLECONTESTANTHTTP POST parameter injection


 

References

Revision History

  • September 6, 2016: Initial release
  • September 13, 2016: Added additional references

This product is provided subject to this Notification and this Privacy & Use policy.


TA16-187A: Symantec and Norton Security Products ... US-CERT
Original release date: July 05, 2016

Systems Affected

All Symantec and Norton branded antivirus products

Overview

Symantec and Norton branded antivirus products contain multiple vulnerabilities. Some of these products are in widespread use throughout government and industry. Exploitation of these vulnerabilities could allow a remote attacker to take control of an affected system.

Description

The vulnerabilities are listed below:

CVE-2016-2207

  • Symantec Antivirus multiple remote memory corruption unpacking RAR [1]

CVE-2016-2208

  • Symantec antivirus products use common unpackers to extract malware binaries when scanning a system. A heap overflow vulnerability in the ASPack unpacker could allow an unauthenticated remote attacker to gain root privileges on Linux or OSX platforms. The vulnerability can be triggered remotely using a malicious file (via email or link) with no user interaction. [2]

CVE-2016-2209 

  • Symantec: PowerPoint misaligned stream-cache remote stack buffer overflow [3]

CVE-2016-2210

  • Symantec: Remote Stack Buffer Overflow in dec2lha library [4]         

CVE-2016-2211

  • Symantec: Symantec Antivirus multiple remote memory corruption unpacking MSPACK Archives [5]

CVE-2016-3644

  • Symantec: Heap overflow modifying MIME messages [6]      

CVE-2016-3645

  • Symantec: Integer Overflow in TNEF decoder [7]       

CVE-2016 -3646

  • Symantec: missing bounds checks in dec2zip ALPkOldFormatDecompressor::UnShrink [8]

 

Impact

The large number of products affected (24 products), across multiple platforms (OSX, Windows, and Linux), and the severity of these vulnerabilities (remote code execution at root or SYSTEM privilege) make this a very serious event. A remote, unauthenticated attacker may be able to run arbitrary code at root or SYSTEM privileges by taking advantage of these vulnerabilities. Some of the vulnerabilities require no user interaction and are network-aware, which could result in a wormable-event.

Solution

Symantec has provided patches or hotfixes to these vulnerabilities in their SYM16-008 [9] and SYM16-010 [10] security advisories.

US-CERT encourages users and network administrators to patch Symantec or Norton antivirus products immediately. While there has been no evidence of exploitation, the ease of attack, widespread nature of the products, and severity of the exploit may make this vulnerability a popular target.

References

Revision History

  • July 5, 2016: Initial Release

This product is provided subject to this Notification and this Privacy & Use policy.


TA16-144A: WPAD Name Collision Vulnerability US-CERT
Original release date: May 23, 2016 | Last revised: June 01, 2016

Systems Affected

  • Windows, OS X, Linux systems, and web browsers with WPAD enabled
  • Networks using unregistered or unreserved TLDs

Overview

Web Proxy Auto-Discovery (WPAD) Domain Name System (DNS) queries that are intended for resolution on private or enterprise DNS servers have been observed reaching public DNS servers [1]. In combination with the new generic top level domain (gTLD) program’s incorporation of previously undelegated gTLDs for public registration, leaked WPAD queries could result in domain name collisions with internal network naming schemes [2] [3]. Opportunistic domain registrants could abuse these collisions by configuring external proxies for network traffic and enabling man-in-the-middle (MitM) attacks across the Internet.

Description

WPAD is a protocol used to ensure all systems in an organization use the same web proxy configuration. Instead of individually modifying configurations on each device connected to a network, WPAD locates a proxy configuration file and applies the configuration automatically.

The use of WPAD is enabled by default on all Microsoft Windows operating systems and Internet Explorer browsers. WPAD is supported but not enabled by default on Mac OS X and Linux-based operating systems, as well as Safari, Chrome, and Firefox browsers.

With the New gTLD program, previously undelegated gTLD strings are now being delegated for public domain name registration [3]. These strings may be used by private or enterprise networks, and in certain circumstances, such as when a work computer is connected from a home or external network, WPAD DNS queries may be made in error to public DNS servers. Attackers may exploit such leaked WPAD queries by registering the leaked domain and setting up MitM proxy configuration files on the Internet.

Other services (e.g., mail and internal web sites) may also perform DNS queries and attempt to automatically connect to supposedly internal DNS names [4].

Impact

Leaked WPAD queries could result in domain name collisions with internal network naming schemes. If an attacker registers a domain to answer leaked WPAD queries and configures a valid proxy, there is potential to conduct man-in-the-middle (MitM) attacks across the Internet.

The WPAD vulnerability is significant to corporate assets such as laptops. In some cases, these assets are vulnerable even while at work, but observations indicate that most assets become vulnerable when used outside an internal network (e.g., home networks, public Wi-Fi networks).

The impact of other types of leaked DNS queries and connection attempts varies depending on the type of service and its configuration.

Solution

US-CERT encourages users and network administrators to implement the following recommendations to provide a more secure and efficient network infrastructure:

  • Consider disabling automatic proxy discovery/configuration in browsers and operating systems unless those systems will only be used on internal networks.
  • Consider using a registered and fully qualified domain name (FQDN) from global DNS as the root for enterprise and other internal namespace.
  • Consider using an internal TLD that is under your control and restricted from registration with the new gTLD program. Note that there is no assurance that the current list of “Reserved Names” from the new gTLD Applicant Guidebook (AGB) will remain reserved with subsequent rounds of new gTLDs [5].
  • Configure internal DNS servers to respond authoritatively to internal TLD queries.
  • Configure firewalls and proxies to log and block outbound requests for wpad.dat files.
  • Identify expected WPAD network traffic and monitor the public namespace or consider registering domains defensively to avoid future name collisions.
  • File a report with ICANN if your system is suffering demonstrable severe harm due to name collision by visiting https://forms.icann.org/en/help/name-collision/report-problems.

References

Revision History

  • May 23, 2016: Initial Release
  • June 1, 2016: Added information on using TLDs restricted from registration with the gTLD program

This product is provided subject to this Notification and this Privacy & Use policy.


TA16-132A: Exploitation of SAP Business Applicati... US-CERT
Original release date: May 11, 2016

Systems Affected

Outdated or misconfigured SAP systems

Overview

At least 36 organizations worldwide are affected by an SAP vulnerability [1]. Security researchers from Onapsis discovered indicators of exploitation against these organizations’ SAP business applications.

The observed indicators relate to the abuse of the Invoker Servlet, a built-in functionality in SAP NetWeaver Application Server Java systems (SAP Java platforms). The Invoker Servlet contains a vulnerability that was patched by SAP in 2010. However, the vulnerability continues to affect outdated and misconfigured SAP systems.

Description

SAP systems running outdated or misconfigured software are exposed to increased risks of malicious attacks.

The Invoker Servlet vulnerability affects business applications running on SAP Java platforms.

SAP Java platforms are the base technology stack for many SAP business applications and technical components, including:

  • SAP Enterprise Resource Planning (ERP),
  • SAP Product Lifecycle Management (PLM),
  • SAP Customer Relationship Management (CRM),
  • SAP Supply Chain Management (SCM),
  • SAP Supplier Relationship Management (SRM),
  • SAP NetWeaver Business Warehouse (BW),
  • SAP Business Intelligence (BI),
  • SAP NetWeaver Mobile Infrastructure (MI),
  • SAP Enterprise Portal (EP),
  • SAP Process Integration (PI),
  • SAP Exchange Infrastructure (XI),
  • SAP Solution Manager (SolMan),
  • SAP NetWeaver Development Infrastructure (NWDI),
  • SAP Central Process Scheduling (CPS),
  • SAP NetWeaver Composition Environment (CE),
  • SAP NetWeaver Enterprise Search,
  • SAP NetWeaver Identity Management (IdM), and
  • SAP Governance, Risk & Control 5.x (GRC).

The vulnerability resides on the SAP application layer, so it is independent of the operating system and database application that support the SAP system.

Impact

Exploitation of the Invoker Servlet vulnerability gives unauthenticated remote attackers full access to affected SAP platforms, providing complete control of the business information and processes on these systems, as well as potential access to other systems.

Solution

In order to mitigate this vulnerability, US-CERT recommends users and administrators implement SAP Security Note 1445998 and disable the Invoker Servlet. For more mitigation details, please review the Onapsis threat report [1].

In addition, US-CERT encourages that users and administrators:

  • Scan systems for all known vulnerabilities, such as missing security patches and dangerous system configurations.
  • Identify and analyze the security settings of SAP interfaces between systems and applications to understand risks posed by these trust relationships.
  • Analyze systems for malicious or excessive user authorizations.
  • Monitor systems for indicators of compromise resulting from the exploitation of vulnerabilities.
  • Monitor systems for suspicious user behavior, including both privileged and non-privileged users.
  • Apply threat intelligence on new vulnerabilities to improve the security posture against advanced targeted attacks.
  • Define comprehensive security baselines for systems and continuously monitor for compliance violations and remediate detected deviations.

These recommendations apply to SAP systems in public, private, and hybrid cloud environments.

Note: The U.S. Government does not endorse or support any particular product or vendor.

References

Revision History

  • May 11, 2016: Initial Release

This product is provided subject to this Notification and this Privacy & Use policy.


TA16-105A: Apple Ends Support for QuickTime for W... US-CERT
Original release date: April 14, 2016

Systems Affected

Microsoft Windows with Apple QuickTime installed

Overview

According to Trend Micro, Apple will no longer be providing security updates for QuickTime for Windows, leaving this software vulnerable to exploitation. [1]

Description

All software products have a lifecycle. Apple will no longer be providing security updates for QuickTime for Windows. [1]

The Zero Day Initiative has issued advisories for two vulnerabilities found in QuickTime for Windows. [2] [3]

Impact

Computer systems running unsupported software are exposed to elevated cybersecurity dangers, such as increased risks of malicious attacks or electronic data loss. Exploitation of QuickTime for Windows vulnerabilities could allow remote attackers to take control of affected systems.

Solution

Computers running QuickTime for Windows will continue to work after support ends. However, using unsupported software may increase the risks from viruses and other security threats. Potential negative consequences include loss of confidentiality, integrity, or availability of data, as well as damage to system resources or business assets. The only mitigation available is to uninstall QuickTime for Windows. Users can find instructions for uninstalling QuickTime for Windows on the Apple Uninstall QuickTime page. [4]

References

Revision History

  • April 14, 2016: Initial Release

This product is provided subject to this Notification and this Privacy & Use policy.


TA16-091A: Ransomware and Recent Variants US-CERT
Original release date: March 31, 2016 | Last revised: July 11, 2016

Systems Affected

Networked Systems

Overview

In early 2016, destructive ransomware variants such as Locky and Samas were observed infecting computers belonging to individuals and businesses, which included healthcare facilities and hospitals worldwide. Ransomware is a type of malicious software that infects a computer and restricts users’ access to it until a ransom is paid to unlock it.

The United States Department of Homeland Security (DHS), in collaboration with Canadian Cyber Incident Response Centre (CCIRC), is releasing this Alert to provide further information on ransomware, specifically its main characteristics, its prevalence, variants that may be proliferating, and how users can prevent and mitigate against ransomware.

Description

WHAT IS RANSOMWARE?

Ransomware is a type of malware that infects computer systems, restricting users’ access to the infected systems. Ransomware variants have been observed for several years and often attempt to extort money from victims by displaying an on-screen alert. Typically, these alerts state that the user’s systems have been locked or that the user’s files have been encrypted. Users are told that unless a ransom is paid, access will not be restored. The ransom demanded from individuals varies greatly but is frequently $200–$400 dollars and must be paid in virtual currency, such as Bitcoin.

Ransomware is often spread through phishing emails that contain malicious attachments or through drive-by downloading. Drive-by downloading occurs when a user unknowingly visits an infected website and then malware is downloaded and installed without the user’s knowledge.

Crypto ransomware, a malware variant that encrypts files, is spread through similar methods and has also been spread through social media, such as Web-based instant messaging applications. Additionally, newer methods of ransomware infection have been observed. For example, vulnerable Web servers have been exploited as an entry point to gain access into an organization’s network.

WHY IS IT SO EFFECTIVE?

The authors of ransomware instill fear and panic into their victims, causing them to click on a link or pay a ransom, and users systems can become infected with additional malware. Ransomware displays intimidating messages similar to those below:

  • “Your computer has been infected with a virus. Click here to resolve the issue.”
  • “Your computer was used to visit websites with illegal content. To unlock your computer, you must pay a $100 fine.”
  • “All files on your computer have been encrypted. You must pay this ransom within 72 hours to regain access to your data.”

PROLIFERATION OF VARIANTS

In 2012, Symantec, using data from a command and control (C2) server of 5,700 computers compromised in one day, estimated that approximately 2.9 percent of those compromised users paid the ransom. With an average ransom of $200, this meant malicious actors profited $33,600 per day, or $394,400 per month, from a single C2 server. These rough estimates demonstrate how profitable ransomware can be for malicious actors.

This financial success has likely led to a proliferation of ransomware variants. In 2013, more destructive and lucrative ransomware variants were introduced, including Xorist, CryptorBit, and CryptoLocker. Some variants encrypt not just the files on the infected device, but also the contents of shared or networked drives. These variants are considered destructive because they encrypt users’ and organizations’ files, and render them useless until criminals receive a ransom.

In early 2016, a destructive ransomware variant, Locky, was observed infecting computers belonging to healthcare facilities and hospitals in the United States, New Zealand, and Germany. It propagates through spam emails that include malicious Microsoft Office documents or compressed attachments (e.g., .rar, .zip). The malicious attachments contain macros or JavaScript files to download Ransomware-Locky files.

Samas, another variant of destructive ransomware, was used to compromise the networks of healthcare facilities in 2016. Unlike Locky, Samas propagates through vulnerable Web servers. After the Web server was compromised, uploaded Ransomware-Samas files were used to infect the organization’s networks.

LINKS TO OTHER TYPES OF MALWARE

Systems infected with ransomware are also often infected with other malware. In the case of CryptoLocker, a user typically becomes infected by opening a malicious attachment from an email. This malicious attachment contains Upatre, a downloader, which infects the user with GameOver Zeus. GameOver Zeus is a variant of the Zeus Trojan that steals banking information and is also used to steal other types of data. Once a system is infected with GameOver Zeus, Upatre will also download CryptoLocker. Finally, CryptoLocker encrypts files on the infected system, and requests that a ransom be paid.

The close ties between ransomware and other types of malware were demonstrated through the recent botnet disruption operation against GameOver Zeus, which also proved effective against CryptoLocker. In June 2014, an international law enforcement operation successfully weakened the infrastructure of both GameOver Zeus and CryptoLocker.

Impact

Ransomware not only targets home users; businesses can also become infected with ransomware, leading to negative consequences, including

  • temporary or permanent loss of sensitive or proprietary information,
  • disruption to regular operations,
  • financial losses incurred to restore systems and files, and
  • potential harm to an organization’s reputation.

Paying the ransom does not guarantee the encrypted files will be released; it only guarantees that the malicious actors receive the victim’s money, and in some cases, their banking information. In addition, decrypting files does not mean the malware infection itself has been removed.

Solution

Infections can be devastating to an individual or organization, and recovery can be a difficult process that may require the services of a reputable data recovery specialist.

US-CERT recommends that users and administrators take the following preventive measures to protect their computer networks from ransomware infection:

  • Employ a data backup and recovery plan for all critical information. Perform and test regular backups to limit the impact of data or system loss and to expedite the recovery process. Note that network-connected backups can also be affected by ransomware; critical backups should be isolated from the network for optimum protection.
  • Use application whitelisting to help prevent malicious software and unapproved programs from running. Application whitelisting is one of the best security strategies as it allows only specified programs to run, while blocking all others, including malicious software.
  • Keep your operating system and software up-to-date with the latest patches. Vulnerable applications and operating systems are the target of most attacks. Ensuring these are patched with the latest updates greatly reduces the number of exploitable entry points available to an attacker.
  • Maintain up-to-date anti-virus software, and scan all software downloaded from the internet prior to executing.
  • Restrict users’ ability (permissions) to install and run unwanted software applications, and apply the principle of “Least Privilege” to all systems and services. Restricting these privileges may prevent malware from running or limit its capability to spread through the network.
  • Avoid enabling macros from email attachments. If a user opens the attachment and enables macros, embedded code will execute the malware on the machine. For enterprises or organizations, it may be best to block email messages with attachments from suspicious sources. For information on safely handling email attachments, see Recognizing and Avoiding Email Scams. Follow safe practices when browsing the Web. See Good Security Habits and Safeguarding Your Data for additional details.
  • Do not follow unsolicited Web links in emails. Refer to the US-CERT Security Tip on Avoiding Social Engineering and Phishing Attacks or the Security Publication on Ransomware for more information.

Individuals or organizations are discouraged from paying the ransom, as this does not guarantee files will be released. Report instances of fraud to the FBI at the Internet Crime Complaint Center.

References

Revision History

  • March 31, 2016: Initial publication
  • May 6, 2016: Clarified guidance on offline backups
  • July 11, 2016: Added link to governmental interagency guidance on ransomware

This product is provided subject to this Notification and this Privacy & Use policy.


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