Name :	Licat.C
Size:	20,480 bytes
Category:	Trojan
Type:	Backdoor
Platform:	Win32
Date of Discovery:	September 22, 2006

Licat.C, a variant of Licat, is a Trojan. Licat.C can send instant messages or contact certain websites to inform malware authors about certain events and allows downloading files on the infected computer. Licat.C tries to connect to certain websites on Internet.

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 him/herself 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 webshop or from our authorised 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's 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 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 command prompt:

DEL C:\WINDOWS\ABC.EXE

and to press Enter. After that an 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 restart a renamed malicious file will no longer be active and it can be easily 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 copy it back to a hard drive it every time it's been renamed or deleted by F-Secure Anti-Virus or by a user. Instructions on how to disable System Restore feature 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 in the future, if any crash or incompatibility issue occurs.


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/

Licat.C arrives on the system as a downloaded file via a link that is spammed through MSN Messenger. Below is a sample message:




It searches for the location of MSN Messenger installed on the system through the following registry key:


When found, it attempts to rename the original MSN Messenger application client to msgs.exe. It then copies itself to the folder using the filename msnmsgr.exe so that it will start each time that MSN Messenger is started by the user. The copy then launches the renamed Messenger file.


Licat.C's backdoor component (some instances are detected as Backdoor.Win32.MSNMaker.v) connects to the following website:


This websites contains links to the following malicious IP address:


It uses a vulnerability in the meta tag, which has a malicious IP address on its content. Vulnerable web browsers will automatically execute the file when this site is accessed.


When this IP address is accessed, it will again download from the following websites and execute other malware on the system using the following filenames:


The downloaded file, sprT.exe, is the one responsible for the pop-up messages spammed through MSN Messenger. This is also detected as IM-Worm.Win32.Licat.c. Below is the pop-up message used:


When this URL link is clicked, a copy of Licat.C will be downloaded on the system.

The two other downloaded files are a trojan dropper (Xinstall.exe) and an adware application (alfa.exe) respectively. They are now detected as
Trojan-Dropper.Win32.PurityScan.ag and not-a-virus:AdWare.Win32.Softomate.q.