Aler is a network worm that was widely mass-mailed with the subject "Latest News about Arafat!!!". The attachments contain a regular JPEG and and custom-crafted EMF file which exploits the EMF (MS04-032) vulnerability. The worm does not use the exploit for propagation. Aler propagates to hosts with weak user passwords.
The clean image looked like this:
The payload of the worm is a multi component TCP proxy trojan.
Once detected, the F-Secure security product will automatically disinfect the suspect file by either deleting it or renaming it.
When the EMF attachment is opened the exploit triggers, which results in a chain-reaction of droppers. The following files are created in the Windows System directory:
- SP00LSV.EXE - main dropper that drops the rest of the files
- Alerter.exe - copy of the main dropper
- Alerter16.exe - copied there during network infection
- SPC.EXE - Backdoor dropper
- SCardSer.exe - Backdoor injector
- comsock.dll (renamed to comwsock.dll) - Backdoor injector
- sockup.dll (renamd to dmsock.dll) - Main backdoor component
- SPTRES.DLL - Network propagation routines
SPTRES.DLL is injected into EXPLORER.EXE, comsock.dll is injected into LSASS.EXE and dmsock.dll is injected into a number of other processes (eg. IEXPLORE.EXE, OUTLOOK.EXE, etc).
The network propagation routine of Aler is very simple. It scans random IP addresses for Windows computers. If it finds one, the worm attempts to connect to it using user credentials from the infected computer as well as a list of predefined passwords (eg. 1234, pass, etc). If the connection is successful the Aler copies the main dropper to the remote computer as
then starts them as a service.
The payload of Aler is a TCP proxy that allows the attacker to initiate network connections through the infected computer. This feature could be used to send SPAM, attack other computers, etc.
The backdoor components of Aler are detected as Backdoor.Win32.Small.bq.
Detection for this malware was published on November 11th, 2004
in the following F-Secure Anti-Virus updates:
Detection Type: PC
Detection for the MS04-032 exploit was added on October 22nd, 2004
in update version
Detection Type: PC
Technical Details: Gergely Erdelyi, November 16th, 2004