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Win32/Srizbi


Srizbi is a trojan that can be remotely controlled to send spam. It also contains rootkit functionality to hide itself.


What to do now

Manual removal is not recommended for this threat. To detect and remove this threat and other malicious software that may have been installed, run a full-system scan with an up-to-date antivirus product such as the Microsoft Safety Scanner (http://go.microsoft.com/fwlink/?LinkId=212742). For more information, see http://www.microsoft.com/protect/computer/viruses/vista.mspx.

Threat behavior

Srizbi is a trojan that can be remotely controlled to send spam. It also contains rootkit functionality to hide itself.
Installation
Srizbi's main component is a device driver (detected as Spammer:WinNT/Srizbi) which is dropped and installed by an executable (detected as TrojanDropper:Win32/Srizbi). Older variants drop the driver with names such as qandr.sys; newer variants use randomly generated names. For example:
  • <system folder>\drivers\QPPVOWSP.sys
 
Newer variants of the dropper also copy themselves to the Windows directory with a random name, for example:
  • %windir%\acbrrrjj.exe
 
These variants also add a registry entry to run the dropper each time Windows starts, for example:
 
Key: HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
Value: ACBRRRJJ (random)
Data: "%windir%\acbrrrjj.exe" (random)
 
The dropper also creates a batch file in the temp directory and runs it. This batch file deletes the original copy of the dropper. Older Srizbi variants use file names such as _it.bat, newer variants use randomly generated file names, for example:
  • %temp%\npb.bat
Payload
Sends Spam
The Srizbi driver connects to a remote server, often on port 4099, to receive instructions and other data, including a list of email addresses to send to, messages to send, fake sender information and mail servers to connect to.
 
Uses Advanced Stealth
Srizbi's device driver hooks several low-level APIs in order to hide its file and registry entries and hinder detection and removal. The driver only hides itself, it does not attempt to hide the dropper’s file or registry entry.
 
Analysis by Tim Liu and Hamish O'Dea

Symptoms

Win32/Srizbi uses advanced stealth in order to hide itself from an affected user, therefore there are no obvious symptoms that indicate the presence of this malware on an affected machine.
 

Prevention

Take the following steps to help prevent infection on your system:
  • Enable a firewall on your computer.
  • Get the latest computer updates for all your installed software.
  • Use up-to-date antivirus software.
  • Use caution when opening attachments and accepting file transfers.
  • Use caution when clicking on links to web pages.
  • Avoid downloading pirated software.
  • Protect yourself against social engineering attacks.
Enable a firewall on your computer
Use a third-party firewall product or turn on the Microsoft Windows Internet Connection Firewall.
To turn on the Windows Firewall in Windows Vista
  1. Click Start, and click Control Panel.
  2. Click Security.
  3. Click Turn Windows Firewall on or off.
  4. Select On.
  5. Click OK.
To turn on the Internet Connection Firewall in Windows XP
  1. Click Start, and click Control Panel.
  2. Click Network and Internet Connections. If you do not see Network and Internet Connections, click Switch to Category View.
  3. Click Change Windows Firewall Settings.
  4. Select On.
  5. Click OK.
Get the latest computer updates
Updates help protect your computer from viruses, worms, and other threats as they are discovered. It is important to install updates for all the software that is installed in your computer. These are usually available from vendor websites.
 
You can use the Automatic Updates feature in Windows to automatically download future Microsoft security updates while your computer is on and connected to the Internet.
To turn on Automatic Updates in Windows Vista
  1. Click Start, and click Control Panel
  2. Click System and Maintainance.
  3. Click Windows Updates.
  4. Select a setting. Microsoft recommends selecting Install updates automatically and choose a time that is convenient for you. If you do not choose Automatic, but you choose to be notified when updates are ready, a notification balloon appears when new downloads are available to install. Click the notification balloon to review and install the updates.
To turn on Automatic Updates in Windows XP
  1. Click Start, and click Control Panel
  2. Click System.
  3. Click Automatic Updates.
  4. Select a setting. Microsoft recommends selecting Automatic. If you do not choose Automatic, but you choose to be notified when updates are ready, a notification balloon appears when new downloads are available to install. Click the notification balloon to review and install the updates.
Use up-to-date antivirus software
Most antivirus software can detect and prevent infection by known malicious software. To help protect you from infection, you should always run antivirus software that is updated with the latest signature files. Antivirus software is available from several sources. For more information, see http://www.microsoft.com/protect/computer/viruses/vista.mspx.
Use caution when opening attachments and accepting file transfers
Exercise caution with e-mail and attachments received from unknown sources, or received unexpectedly from known sources.  Use extreme caution when accepting file transfers from known or unknown sources.
Use caution when clicking on links to web pages
Exercise caution with links to web pages that you receive from unknown sources, especially if the links are to a web page that you are not familiar with or are suspicious of. Malicious software may be installed in your system simply by visiting a web page with harmful content.
Avoid downloading pirated software
Threats may also be bundled with software and files that are available for download on various torrent sites. Downloading "cracked" or "pirated" software from these sites carries not only the risk of being infected with malware, but is also illegal. For more information. please see our article 'The risks of obtaining and using pirated software'.
Protect yourself from social engineering attacks
While attackers may attempt to exploit vulnerabilities in hardware or software in order to compromise a system, they also attempt to exploit vulnerabilities in human behavior in order to do the same. When an attacker attempts to take advantage of human behavior in order to persuade the affected user to perform an action of the attacker's choice, it is known as 'social engineering'. Essentially, social engineering is an attack against the human interface of the targeted system. For more information, please see our article 'What is social engineering?'. 

Alert level: Severe
This entry was first published on: Jan 30, 2009
This entry was updated on: Apr 17, 2011

This threat is also detected as:
  • Rootkit.Win32.Agent.ea (Kaspersky)
  • Generic.dx (McAfee)
  • Troj/RKAgen-Fam (Sophos)
  • Trojan.Srizbi (Symantec)