F-Secure Malware Information Pages: Exploit:W32/Ani.C

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F-Secure Malware Information Pages: Exploit:W32/Ani.C

[Summary] \| [Disinfection] \| [Detailed Description] \| [Detection]
Name :	Exploit:W32/Ani.C
Alias:	Exploit.Win32.IMG-ANI.c, Trojan-Downloader.Win32.Ani.g, TROJ_ANICMOO.AX, Troj/Animoo-U, Exploit-ANIfile.c trojan, Exploit:W32/Ani.D, Exploit:W32/Ani.E
Size:	Random
Type:	Exploit, Trojan-Downloader
Category:	Malware
Platform:	W32
Date of Discovery:	March 29, 2007

Radar

Summary

Exploit:W32/Ani.C is a trojan that exploits a vulnerability in Windows animated cursor handling, .ANI files, in order to download and install other Malware to the system.

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Disinfection

Automatic Disinfection

Usually standalone malware (backdoors, worms, trojans, etc.) is automatically removed by F-Secure Anti-Virus (FSAV) starting from version 5.40. Malware files get automatically renamed by FSAV, so they can not be started any more. In some rare cases, when automatic disinfection is not possible, a user can select disinfection action by themselves to make FSAV rename or delete an infected file. In some special cases it is recommended to use specific disinfection tools provided by F-Secure. They can be downloaded from our ftp site:

ftp://ftp.f-secure.com/anti-virus/tools/

F-Secure Anti-Virus can be purchased from our web shop or from our authorized distributors. A trial version F-Secure Anti-Virus, limited to 30 days, can be downloaded from our website:

http://www.f-secure.com/download-purchase/

All the latest versions of FSAV can download anti-virus database updates automatically. However, these updates can be also downloaded and installed manually from our web or ftp sites:

http://www.f-secure.com/download-purchase/updates.shtml

Manual Disinfection

To manually disinfect standalone malware (backdoors, worms, trojans, etc.) it is usually enough to delete all infected files from a computer and to restart it. Active malware files are usually locked by operating system so different disinfection approaches are required for different operating systems.
Please note that manual disinfection is a risky process, so it is recommended only for advanced users.

If Windows 95, 98 and ME operating system is used, it is recommended to restart a computer from a bootable system diskette and to delete an infected file from the command prompt. For example, if a malicious file named ABC.EXE is located in Windows folder, it is usually enough to type the following command at the command prompt:

DEL C:\WINDOWS\ABC.EXE

and to press Enter. After that, the infected file will be gone. If Windows NT, 2000 or XP is used, a malicious file has to be renamed with a different extension (for example .VIR) and then a system has to be restarted. After restarting, a renamed malicious file will no longer be active and it can be deleted manually.

Malware Disinfection Tools

F-Secure provides disinfection tools for certain malware. These tools can be downloaded from this webpage:

http://www.f-secure.com/download-purchase/tools.shtml

ftp://ftp.f-secure.com/anti-virus/tools/

Windows System Restore Issues

If Windows ME or XP is used, it is recommended to disable System Restore feature of these operating systems to prevent a computer from re-infection by an already removed malware. The fact is that System Restore feature of these operating systems might save an infected file into the special folder and copies it back to a hard drive every time it has been renamed or deleted by F-Secure Anti-Virus or by a user. Instructions on how to disable System Restore features are here:

Windows ME:
http://www.f-secure.com/v-descs/sfc_dis.shtml

Windows XP:
http://www.f-secure.com/v-descs/sfc_dis1.shtml

It is recommended to re-enable System Restore after disinfection in order to restore stable system configuration if any crash or incompatibility issue occurs in the future.

Failed Disinfection

In some cases F-Secure Anti-Virus might not disinfect a system automatically. In this case please visit our Support pages:

http://support.f-secure.com/enu/home/virusproblem/howtoclean/

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Detailed Description

Ani.C is a trojan that takes advantage of a Vulnerability in Windows Animated Cursor Handling (Security Advisory 935423), in order to download other malicious files from the Internet.

These malicious animated cursor (.ANI) files can be hosted on websites and can trigger code execution upon visiting such sites. They can also be embedded in specially crafted e-mails or attachments within the e-mail that upon reading or previewing can cause the system to execute the code.

This trojan was seen hosted at the following site:

http://newasp.com.cn/[REMOVED].jpg

Other sites found also links or loads the malicious .ANI file:

http://newasp.com.cn/[removed].htm
http://bc0.cn/[removed].js

Upon successful execution, this trojan may download other malware via the Internet and execute it on the system. Below are the download sites used:

http://newasp.com.cn/[removed].exe - Trojan-PSW:W32/Agent.IM
http://61.218.38.35/images/[removed].exe -
Trojan-Downloader:Win32/Tiny.GG
http://220.71.76.xxx/wincf.exe - Trojan-Downloader:W32/Small.EKV

More information about this malware can be found from our weblog post.

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Detection

F-Secure Anti-Virus detects this malware with the following updates:

[FSAV_Database_Version]

Version = 2007-03-29_09.

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F-Secure Corporation

Last Modified: March 30, 2007