Backdoor:OSX/Imuler.A

Classification

Type:Backdoor

Summary

Backdoor:OSX/Imuler.A contacts a remote server for instructions; it may then steal files or capture a screenshot of the infected computer system, which is then forwarded to the remote server.

Removal

The F-Secure security product will automatically remove the file.

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

Backdoor:OSX/Imuler.A may be variously dropped or installed onto a system by variants in the Trojan-Dropper:OSX/Revir family.

Installation

Upon execution, the backdoor drops a copy of itself to the following location:

~/library/LaunchAgents/checkvir

It creates the following launch point:

~/library/LaunchAgents/checkvir.plist

It also creates the following file, containing its Command and Control, or C&C, server:

~/library/.confback

Network Connections

The malware downloads a command line tool from the external site

http://%server%/CurlUpload

Note: As of this writing, %server% can be any of the following -

www. sugarsbutters.com
www. teklimakan.org

The downloaded file is then saved as:

/tmp/CurlUpload

The malware obtains the external IP address and current time by connecting to the following URLs:

http://%server%/cgi-mac/whatismyip.cgi
http://%server%/cgi-mac/2wmthetime.cgi

It collects system information, then uploads the collected information to the following location:

http://%server%/cgi-mac/2wmrecvdata.cgi

Collected information includes the following:

Internal IP
External IP
Username of the infected user
Time of last execution
Kernel version of the infected host

The malware then makes a HTTP POST request containing the%botid% to the following URLs, presumably to report that the infected host is ready to receive commands:

http://%server%/cgi-mac/2wmcheckdir.cgi
http://%server%/cgi-mac/2wmsetstatus.cgi

Backdoor

The malware contacts a remote server (the C&C server) to get its instructions. The URL is based on the following formula:

http://%server%/users/%botid%/xnocz1

Where:

%botid% - Is composed of:%user%%pad%%mac%

Based on the instructions received, the backdoor is capable of performing the following actions:

Download additional files
Execute files on the infected host
Collect system information then upload to the C&C
Collect files to an archive, then upload it to the C&C server
Capture an image of the computer screen, then upload it to the C&C

After receiving the commands, the malware makes a HTTP HEAD request the to following URL, presumably to report that the infected host has successfully receive the commands: