1. Symantec/
  2. Security Response/
  3. Backdoor.Regin


Risk Level 1: Very Low

December 12, 2013
January 16, 2017 11:22:29 AM
Infection Length:
Systems Affected:
Backdoor.Regin is an extremely complex back door Trojan that enables stealthy surveillance activities. It can be customized with a wide range of different capabilities, which can be deployed depending on the target. It is a multi-staged, modular threat, meaning that it has a number of components, each depending on each other to perform attack operations.

When the Trojan is executed, it creates the following kernel drivers:
  • usbclass.sys
  • adpu160.sys

Next, the Trojan creates the following files which contain encrypted virtual file systems (EVSFs)
  • %System%\config\SystemLog.evt
  • %System%\config\SecurityLog.evt
  • %System%\config\ApplicationLog.evt
  • %Windir%\ime\imesc5\dicts\pintlgbp.imd
  • %Windir%\ime\imesc5\dicts\pintlgbs.imd

The Trojan then creates the following files:
  • msdcsvc.dat
  • msrdc64.dat
  • ApplicationLog.dat
  • %System%\config\SystemAudit.Evt
  • %Windir%\system32\winhttpc.dll
  • %Windir%\system32\wshnetc.dll
  • %Windir%\SysWow64\wshnetc.dll
  • %Windir%\system32\svcstat.exe
  • %Windir%\system32\svcsstat.exe

Next, the Trojan encrypts data and loads components of itself from extended attributes of the following folders:
  • %Windir%
  • %Windir%\cursors
  • %Windir%\fonts
  • %Windir%\System32
  • %Windir%\System32\drivers

The Trojan then creates the following registry subkeys:
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4F20E605-9452-4787-B793-D0204917CA58}
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4F20E605-9452-4787-B793-D0204917CA5A}
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\RestoreList\VideoBase

The attacker controls the Trojan using the following transport protocols:
  • Internet Control Message Protocol (ICMP): Payload information can be encoded and embedded in place of legitimate ICMP/ping data.
  • User Datagram Protocol (UDP): Raw UDP payload
  • Transmission Control Protocol (TCP): Raw TCP payload
  • HTTP: Payload information can be encoded and embedded within cookie data under the names SESSID, SMSWAP, TW, WINKER, TIMESET, LASTVISIT, AST.NET_SessionId, PHPSESSID, or phpAds_d. This information can be combined with another cookie for validation under the names USERIDTK, UID, GRID, UID=PREF=ID, TM, __utma, LM, TMARK, VERSION, or CURRENT

The Trojan may then perform the following actions:
  • Sniff low-level network traffic
  • Exfiltrate data through various channels (TCP, UDP, ICMP, and HTTP)
  • Gather computer information
  • Steal passwords
  • Gather process and memory information
  • Navigate through file system
  • Perform low-level forensics operations, such as retrieving files that were deleted
  • Manipulate user interface (UI), such as conducting remote mouse point-and-click activities and capturing screenshots
  • Enumerate Internet Information Services (IIS) web servers and steal logs
  • Sniff GSM BSC administration network traffic


Symantec Security Response encourages all users and administrators to adhere to the following basic security "best practices":

  • Use a firewall to block all incoming connections from the Internet to services that should not be publicly available. By default, you should deny all incoming connections and only allow services you explicitly want to offer to the outside world.
  • Enforce a password policy. Complex passwords make it difficult to crack password files on compromised computers. This helps to prevent or limit damage when a computer is compromised.
  • Ensure that programs and users of the computer use the lowest level of privileges necessary to complete a task. When prompted for a root or UAC password, ensure that the program asking for administration-level access is a legitimate application.
  • Disable AutoPlay to prevent the automatic launching of executable files on network and removable drives, and disconnect the drives when not required. If write access is not required, enable read-only mode if the option is available.
  • Turn off file sharing if not needed. If file sharing is required, use ACLs and password protection to limit access. Disable anonymous access to shared folders. Grant access only to user accounts with strong passwords to folders that must be shared.
  • Turn off and remove unnecessary services. By default, many operating systems install auxiliary services that are not critical. These services are avenues of attack. If they are removed, threats have less avenues of attack.
  • If a threat exploits one or more network services, disable, or block access to, those services until a patch is applied.
  • Always keep your patch levels up-to-date, especially on computers that host public services and are accessible through the firewall, such as HTTP, FTP, mail, and DNS services.
  • Configure your email server to block or remove email that contains file attachments that are commonly used to spread threats, such as .vbs, .bat, .exe, .pif and .scr files.
  • Isolate compromised computers quickly to prevent threats from spreading further. Perform a forensic analysis and restore the computers using trusted media.
  • Train employees not to open attachments unless they are expecting them. Also, do not execute software that is downloaded from the Internet unless it has been scanned for viruses. Simply visiting a compromised Web site can cause infection if certain browser vulnerabilities are not patched.
  • If Bluetooth is not required for mobile devices, it should be turned off. If you require its use, ensure that the device's visibility is set to "Hidden" so that it cannot be scanned by other Bluetooth devices. If device pairing must be used, ensure that all devices are set to "Unauthorized", requiring authorization for each connection request. Do not accept applications that are unsigned or sent from unknown sources.
  • For further information on the terms used in this document, please refer to the Security Response glossary.
Summary| Technical Details| Removal

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2016 Internet Security Threat Report, Volume 21
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