Summary
This worm spreads though the IRC network by sending a link to a web page which contains an exploit and runs a script. This script drops and runs a file called browsercheck.exe
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 worm's life-cycle is as follows:
A URL is posted in an IRC channel, the URL has the following format (it has been partially modified on purpose).
https://www.[removed].at/[removed]/show.php?f=drunkchicks.jpg
and the message on the channel:
https://www.[removed].at/[removed]/show.php?f=drunkchicks.jpg LOL
The URL contains a HTML file with code taking advantage of an Internet Explorer vulnerability. When a user clicks or enters the URL in Internet Explorer, a VBS script will be downloaded from:
https://www.[removed].at/[removed]/drunkchicks.php
and executed. This script will open a window outside the user's desktop, aiming at remaining unnoticed. It contains several strings with a comma separated list of octets which, through a very simple decoding, are written into a file on the path:
C:\browsercheck.exe
This executable has a length of 3584 bytes. This executable will use the Dynamic Data Exchange Management Library provided by the Windows user interface API, to communicate with an existing and running IRC client on the computer. (This functionality might be limited to the Internet Relay Chat client mIRC).
If the communication is successful, it will use the IRC client to send a command which will perform the following actions:
- It will post to the channel the URL containing the exploit plus the text " LOL".
- It will attempt to set the topic of the first channel the user joined to the text containing the URL.
- It will attempt to set the topic of the second channel the user joined to the text containing the URL.
- Sets the user's nick as registered.
The VBS script will drop the executable into the users' system. That will be the only modification made to the user's computer. The dropped executable won't make any changes to the system's configuration, nor it will be executed on restart. It will only be run from the VBS script.
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