Threat Description



Aliases: Agent.aa, Trojan-PSW.Win32.Agent.aa, Bancos.NL
Category: Malware
Type: Trojan
Platform: W32


Agent.aa is a data stealing trojan that tries to steal account information from the infected computer. It steals cached credientials from the system and monitors active web browsers, logging keystrokes sent to online banks. It can also take screenshots of browser windows.


Automatic action

Once detected, the F-Secure security product will automatically disinfect the suspect file by either deleting it or renaming it.


Detailed instructions for F-Secure security products are available in the documentation found in the Downloads section of our Home - Global site.

You may also refer to the Knowledge Base on the F-Secure Community site for further assistance.

Technical Details

Installation to system

Agent.aa file is a PE executable image, packed with executable compressor PECompact. The packed size is about 37 kilobytes.

When run, the trojan copies itself under Windows directory using the name 'mscsvc.exe'. It installs the following registry key to make sure it will be executed next time the system is started:

 [HKLM\Software\Microsoft\Windows\CurrentVersion\Run]  "mscsvc.exe" = "%WinDir%\mscsvc.exe"  

For example, %WinDir% is 'C:\Windows' in default installation of Windows XP.

Data stealing

The trojan monitors active Internet Explorer instances. When a web page containing certain domain names is visited, the trojan logs data from the web page, including key strokes. Domain names are mostly online banks. It may also take screenshots of browser windows while visiting these domains.

Here is the list of domain names that are monitored (in alphabetical order):

Note that it doesn't automatically mean that the listed online banks are affected. Most online banks use proper one-time password authentication schemes, and are thus not in danger.

The trojan also tries to fetch cached accounting information from the infected computer, such as

  • Internet Explorer FTP usernames/passwords
  • Outlook Account Manager Passwords
  • HTTP usernames/passwords
  • IMAP, POP3 usernames/passwords

Also, some generic system information, such as installed software, running process etc. are gathered from the infected system.

Stealed data is sent to server '' using HTTP POST requests.


Detection Type: PC
Database: 2005-04-26_01

Technical Details:Jarkko Turkulainen; May 03th, 2005


Suspect a file or URL was wrongly detected? Submit a sample to our Labs for analysis

Submit Now

Disinfect your PC

F-Secure Anti-Virus will disinfect your PC and remove all harmful files

Learn More