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National Cyber Awareness System: 07/31/2014 07:30 AM EDT
Original release date: July 31, 2014 | Last revised: August 18, 2014
Systems AffectedPoint-of-Sale Systems
OverviewThis advisory was prepared in collaboration with the National Cybersecurity and Communications Integration Center (NCCIC), United States Secret Service (USSS), Financial Sector Information Sharing and Analysis Center (FS-ISAC), and Trustwave Spiderlabs, a trusted partner under contract with the USSS. The purpose of this release is to provide relevant and actionable technical indicators for network defense. Recent investigations revealed that malicious actors are using publicly available tools to locate businesses that use remote desktop applications. Remote desktop solutions like Microsoft's Remote Desktop [1] Apple Remote Desktop,[2] Chrome Remote Desktop,[3] Splashtop 2,[4] Pulseway[5], and LogMeIn[6] offer the convenience and efficiency of connecting to a computer from a remote location. Once these applications are located, the suspects attempted to brute force the login feature of the remote desktop solution. After gaining access to what was often administrator or privileged access accounts, the suspects were then able to deploy the point-of-sale (PoS) malware and subsequently exfiltrate consumer payment data via an encrypted POST request. USSS, NCCIC/US-CERT and Trustwave Spiderlabs have been working together to characterize newly identified malware dubbed "Backoff", associated with several PoS data breach investigations. At the time of discovery and analysis, the malware variants had low to zero percent anti-virus detection rates, which means that fully updated anti-virus engines on fully patched computers could not identify the malware as malicious. Similar attacks have been noted in previous PoS malware campaigns [7] and some studies state that targeting the Remote Desktop Protocol with brute force attacks is on the rise.[8] A Mitigation and Prevention Strategies section is included to offer options for network defenders to consider. Description“Backoff” is a family of PoS malware and has been discovered recently. The malware family has been witnessed on at least three separate forensic investigations. Researchers have identified three primary variants to the “Backoff” malware including 1.4, 1.55 (“backoff”, “goo”, “MAY”, “net”), and 1.56 (“LAST”). These variations have been seen as far back as October 2013 and continue to operate as of July 2014. In total, the malware typically consists of the following four capabilities. An exception is the earliest witnessed variant (1.4) which does not include keylogging functionality. Additionally, 1.55 ‘net’ removed the explorer.exe injection component:
The malicious stub that is injected into explorer.exe is responsible for persistence in the event the malicious executable crashes or is forcefully stopped. The malware is responsible for scraping memory from running processes on the victim machine and searching for track data. Keylogging functionality is also present in most recent variants of “Backoff”. Additionally, the malware has a C2 component that is responsible for uploading discovered data, updating the malware, downloading/executing further malware, and uninstalling the malware. Variants Based on compiled timestamps and versioning information witnessed in the C2 HTTP POST requests, “Backoff” variants were analyzed over a seven month period. The five variants witnessed in the “Backoff” malware family have notable modifications, to include: 1.55 “backoff”
1.55 “goo”
1.55 “MAY”
1.55 “net”
1.56 “LAST”
Command & Control Communication All C2 communication for “Backoff” takes place via HTTP POST requests. A number of POST parameters are included when this malware makes a request to the C&C server.
The ‘id’ parameter is stored in the following location, to ensure it is consistent across requests:
If this key doesn’t exist, the string will be generated and stored. Data is encrypted using RC4 prior to being encoded with Base64. The password for RC4 is generated from the ‘id’ parameter, a static string of ‘jhgtsd7fjmytkr’, and the ‘ui’ parameter. These values are concatenated together and then hashed using the MD5 algorithm to form the RC4 password. In the above example, the RC4 password would be ‘56E15A1B3CB7116CAB0268AC8A2CD943 (The MD5 hash of ‘vxeyHkSjhgtsd7fjmytkrJosh @ PC123456). File Indicators: The following is a list of the Indicators of Compromise (IOCs) that should be added to the network security to search to see if these indicators are on their network. 1.4 Packed MD5: 927AE15DBF549BD60EDCDEAFB49B829E Unpacked MD5: 6A0E49C5E332DF3AF78823CA4A655AE8 Install Path: %APPDATA%\AdobeFlashPlayer\mswinsvc.exe Mutexes: uhYtntr56uisGst uyhnJmkuTgD Files Written: %APPDATA%\mskrnl %APPDATA%\winserv.exe %APPDATA%\AdobeFlashPlayer\mswinsvc.exe Static String (POST Request): zXqW9JdWLM4urgjRkX Registry Keys: HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\identifier HKCU\ SOFTWARE \Microsoft\Windows\CurrentVersion\Run\Windows NT Service User-Agent: Mozilla/4.0 URI(s): /aircanada/dark.php 1.55 “backoff” Packed MD5: F5B4786C28CCF43E569CB21A6122A97E Unpacked MD5: CA4D58C61D463F35576C58F25916F258 Install Path: %APPDATA%\AdobeFlashPlayer\mswinhost.exe Mutexes: Undsa8301nskal uyhnJmkuTgD Files Written: %APPDATA%\mskrnl %APPDATA%\winserv.exe %APPDATA%\AdobeFlashPlayer\mswinhost.exe %APPDATA%\AdobeFlashPlayer\Local.dat %APPDATA%\AdobeFlashPlayer\Log.txt Static String (POST Request): ihasd3jasdhkas Registry Keys: HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\identifier HKCU\ SOFTWARE \Microsoft\Windows\CurrentVersion\Run\Windows NT Service User-Agent: Mozilla/5.0 (Windows NT 6.1; rv:24.0) Gecko/20100101 Firefox/24.0 URI(s): /aero2/fly.php 1.55 “goo” Pa cked MD5: 17E1173F6FC7E920405F8DBDE8C9ECAC Unpacked MD5: D397D2CC9DE41FB5B5D897D1E665C549 Install Path: %APPDATA%\OracleJava\javaw.exe Mutexes: nUndsa8301nskal nuyhnJmkuTgD Files Written: %APPDATA%\nsskrnl %APPDATA%\winserv.exe %APPDATA%\OracleJava\javaw.exe %APPDATA%\OracleJava\Local.dat %APPDATA%\OracleJava\Log.txt Static String (POST Request): jhgtsd7fjmytkr Registry Keys: HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\identifier HKCU\ SOFTWARE \Microsoft\Windows\CurrentVersion\Run\Windows NT Service User-Agent: URI(s): /windows/updcheck.php 1.55 “MAY” Packed MD5: 21E61EB9F5C1E1226F9D69CBFD1BF61B Unpacked MD5: CA608E7996DED0E5009DB6CC54E08749 Install Path: %APPDATA%\OracleJava\javaw.exe Mutexes: nUndsa8301nskal nuyhnJmkuTgD Files Written: %APPDATA%\nsskrnl %APPDATA%\winserv.exe %APPDATA%\OracleJava\javaw.exe %APPDATA%\OracleJava\Local.dat %APPDATA%\OracleJava\Log.txt Static String (POST Request): jhgtsd7fjmytkr Registry Keys: HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\identifier HKCU\ SOFTWARE \Microsoft\Windows\CurrentVersion\Run\Windows NT Service User-Agent: URI(s): /windowsxp/updcheck.php 1.55 “net” Packed MD5: 0607CE9793EEA0A42819957528D92B02 Unpacked MD5: 5C1474EA275A05A2668B823D055858D9 Install Path: %APPDATA%\AdobeFlashPlayer\mswinhost.exe Mutexes: nUndsa8301nskal Files Written: %APPDATA%\AdobeFlashPlayer\mswinhost.exe %APPDATA%\AdobeFlashPlayer\Local.dat %APPDATA%\AdobeFlashPlayer\Log.txt Static String (POST Request): ihasd3jasdhkas9 Registry Keys: HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\identifier HKCU\ SOFTWARE \Microsoft\Windows\CurrentVersion\Run\Windows NT Service User-Agent: URI(s): /windowsxp/updcheck.php 1.56 “LAST” Packed MD5: 12C9C0BC18FDF98189457A9D112EEBFC Unpacked MD5: 205947B57D41145B857DE18E43EFB794 Install Path: %APPDATA%\OracleJava\javaw.exe Mutexes: nUndsa8301nskal nuyhnJmkuTgD Files Written: %APPDATA%\nsskrnl %APPDATA%\winserv.exe %APPDATA%\OracleJava\javaw.exe %APPDATA%\OracleJava\Local.dat %APPDATA%\OracleJava\Log.txt Static String (POST Request): jhgtsd7fjmytkr Registry Keys: HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\identifier HKCU\ SOFTWARE \Microsoft\Windows\CurrentVersion\Run\Windows NT Service HKLM\ SOFTWARE \Microsoft\Windows\CurrentVersion\Run\Windows NT Service HKCU\SOFTWARE\Microsoft\Active Setup\Installed Components\{B3DB0D62-B481-4929-888B-49F426C1A136}\StubPath HKLM\SOFTWARE\Microsoft\Active Setup\Installed Components\{B3DB0D62-B481-4929-888B-49F426C1A136}\StubPath User-Agent: Mozilla/5.0 (Windows NT 6.1; rv:24.0) Gecko/20100101 Firefox/24.0 URI(s): /windebug/updcheck.php ImpactThe impact of a compromised PoS system can affect both the businesses and consumer by exposing customer data such as names, mailing addresses, credit/debit card numbers, phone numbers, and e-mail addresses to criminal elements. These breaches can impact a business’ brand and reputation, while consumers’ information can be used to make fraudulent purchases or risk compromise of bank accounts. It is critical to safeguard your corporate networks and web servers to prevent any unnecessary exposure to compromise or to mitigate any damage that could be occurring now. SolutionAt the time this advisory is released, the variants of the “Backoff’ malware family are largely undetected by anti-virus (AV) vendors. However, shortly following the publication of this technical analysis, AV companies will quickly begin detecting the existing variants. It’s important to maintain up‐to‐date AV signatures and engines as new threats such as this are continually being added to your AV solution. Pending AV detection of the malware variants, network defenders can apply indicators of compromise (IOC) to a variety of prevention and detection strategies.[9],[10],[11] IOCs can be found above. The forensic investigations of compromises of retail IT/payment networks indicate that the network compromises allowed the introduction of memory scraping malware to the payment terminals. Information security professionals recommend a defense in depth approach to mitigating risk to retail payment systems. While some of the risk mitigation recommendations are general in nature, the following strategies provide an approach to minimize the possibility of an attack and mitigate the risk of data compromise: Remote Desktop Access
Network Security
Cash Register and PoS Security
References
Revision History
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