Virus.Multi.Angela

Class Virus
Platform Multi
Description

Technical Details

This is a multipartite virus infecting hard drive MBR sector, floppy drives
boot sector, DOS EXE file as well as spreading via IRC channels by
infecting the mIRC client, as well as mailing itself by using MS Outlook.

The virus may appear on a computer on an infected floppy disk, as an infected DOS
EXE file, or as an infected attachment in an e-mail message.

The virus has no payloads and does not manifest itself in any way except
one – it deletes the file:

C:WINDOWSSYSTEMIOSUBSYSHSFLOP.PDR

The virus needs to delete this file to force Windows to operate the floppy-disk sectors by using an old-style INT 13h way (this is necessary for thevirus to
run its disk infection and stealth routines, see below).

Booting from an infected disk

Upon loading from an infected disk, the virus hooks INT 13h (disk access) and INT
1Ch (timer). By using a timer hook, the virus waits until a system is booting
up, then hooks INT 21h (DOS functions) and infects DOS EXE files that are
executed. By hooking INT 13h, the virus gets access to floppy disks and
infects their boot sectors. The virus also realizes {stealth:Stealth} a
function upon accessing infected disk sectors.

Infected DOS EXE file run

Upon being run from an infected DOS EXE file, the virus infects the hard drive’s MBR
sector, creates and registers its DOS EXE dropper, creates a VBS script
program to spread with e-mail, and creates an mIRC script to be sent to IRC
channels.

The virus dropper has the ANGELA.EXE name and is created in the C:WINDOWSSYSTEM
directory (If Windows is installed in another directory, the virus
cannot spread to IRC and in e-mail). This file is registered to be run upon
each rebooting in the C:AUTOEXEC.BAT file. The virus writes a command to
there to run this file upon each reboot, and adds comments to that file:

@ECHO OFF
c:windowssystemangela.exe
REM – DO NOT REMOVE!

The virus dropper does the same as the virus does in infected DOS EXE file does;
i.e., if any of the virus components (VBS or mIRC script) are deleted, the virus
will re-create it upon the next reboot.

Mailing

The virus creates the ANGELA.VBS file in the Windows start-up directory, and
as a result, this script is activated upon each Windows boot-up. The program in
the script access MS Outlook obtains address book records, and sends a virus
copy (the ANGELA.EXE dropper) to the first 20 addresses that are found there.
The message has:

Subject: Finally found it!
Body: Here are the files you asked me for…
Attachment name: angela.exe

The script then deletes its VBS file, and there are no more infected
messages sent during the same Windows seance, but upon he tnext computer reboot,
the ANGELA.EXE dropper will be activated from AUTOEXEC.BAT, and it will
re-create the VBS mailing routine.

Infecting IRC channels

The virus creates the SCRIPT.INI file in the C:MIRC directory. This script
sends an ANGELA.EXE dropper to all users that join the infected IRC channel.