Rule:

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Sid:
120

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Summary:
Infector is a Trojan Horse.

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Impact:
Possible theft of data via download, upload of files, execution of files
and reboot the targeted machine.

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Detailed Information:
This Trojan affects the following operating systems:

	Windows 95
	Windows 98
	Windows ME

The Trojan changes system registry settings to add the Infector sever to
programs normally started on boot. Due to the nature of this Trojan it 
is unlikely that the attacker's client IP address has been spoofed.

	SID	Message
	---	-------
	117	Infector 1.x
	120	Infector 1.6 Server to Client
	121	Infector 1.6 Client to Server Connection Request

This Trojan is commonly used to install other Trojan programs.

The Trojan also makes changes to the system registry and win.ini file.

Notification of an active server is achieved via IRC or ICQ.

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Attack Scenarios:
This Trojan may be delivered to the target in a number of ways. This 
event is indicative of an existing infection being activated. Initial 
compromise can be in the form of a Win32 installation program that may 
use the extension ".jpg" or ".bmp" when delivered via e-mail for 
example.

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Ease of Attack:
This is Trojan activity, the target machine may already be compromised. 
Updated virus definition files are essential in detecting this Trojan.

The Trojan server is located at <drive>:\WINDOWS\Apxil32.exe a backup 
copy is made and usually named D3x32.drv.

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False Positives:
None Known

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False Negatives:
None Known

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Corrective Action:

Edit the system registry to remove the extra keys or restore a 
previously known good copy of the registry.

Affected registry keys are:

	HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\
	HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunServices

Registry keys added are:

	apxil32 = apxil32.exe

Removal of this entry is required.

Delete the file <drive>:\WINDOWS\Apxil32.exe

Ending the Trojan process is also necessary. A reboot of the infected 
machine is recommended.

A change is also made to the win.ini file, the line run=apxil32.exe 
apxil32.exe is added and should be deleted.

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Contributors:
Original Rule Writer Max Vision <vision@whitehats.com>
Sourcefire Research Team
Nigel Houghton <nigel.houghton@sourcefire.com>

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Additional References:

Whitehats arachNIDS
http://www.whitehats.com/info/IDS315
http://www.whitehats.com/info/IDS502
http://www.whitehats.com/info/IDS503

Diamond Computer Systems Security Advisory
http://www.diamondcs.com.au/web/alerts/infector.htm

Megasecurity:
http://www.megasecurity.org/trojans/i/infector/Infector_all.html

Simovits:
http://www.simovits.com/trojans/tr_data/y1627.html

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