Trojan-Downloader:W32/Agent.ACL

Classification

Category :

Malware

Type :

Trojan-Downloader

Aliases :

Trojan-Downloader:W32/Agent.ACL

Summary

This trojan is usually dropped by other malware installation packages. On execution, it downloads and execute another trojan file on the system.

Removal

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.

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 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.

Technical Details

This Trojan usually arrives on the system as a dropped file of Trojan-Downloader:W32/Agent.EOA.However, this doesn't normally exists as a "physical" file since this malware's executable image is usually just injected into the iexplore process by Trojan-Downloader:W32/Agent.EOA. Running in the process context of Internet Explorer, this Trojan increases the chance of getting through the system firewall since it is most likely that Internet Explorer has already been included by the user to the list of approved applications that can pass through the firewall. To ensure only an instance of itself is running, it checks for the malware-created mutex "k4j.32H_f7z_Z6e.g8G0".The malware then retrieves the system's basic disk properties such as volume information, serial and volume type, the computer's IP address, and running antivirus processes that match its list. It then use this data as a parameter to an HTTP request to download a set of malware from a remote server.

Based on the characteristic being checked by the malware, the individual executable image included in the downloaded payload can either be dropped as a single file in computer's temporary folder and then executed as an independent process, or the image will be injected into a hidden Internet Explorer process space. As of current testing, the downloaded payload usually contains two executable images which are detected as:

  • Rootkit:W32/Agent.Ey and Email-Worm:W32/Agent.BC