Agent.aa, Trojan-PSW.Win32.Agent.aa, Bancos.NL


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

Based on the settings of your F-Secure security product, it will either move the file to the quarantine where it cannot spread or cause harm, or remove it.

Suspect a file is incorrectly detected (a False Positive)?

A False Positive is when a file is incorrectly detected as harmful, usually because its code or behavior resembles known harmful programs. A False Positive will usually be fixed in a subsequent database update without any action needed on your part. If you wish, you may also:

  • Check for the latest database updates

    First check if your F-Secure security program is using the latest detection database updates, then try scanning the file again.

  • Submit a sample

    After checking, if you still believe the file is incorrectly detected, you can submit a sample of it for re-analysis.

    NOTE If the file was moved to quarantine, you need to collect the file from quarantine before you can submit it.

  • Exclude a file from further scanning

    If you are certain that the file is safe and want to continue using it, you can exclude it from further scanning by the F-Secure security product.

    Note You need administrative rights to change the settings.

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User Guide

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Submit a sample

Submit a file or URL for further analysis.

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:

"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.