A spam message containing link that leads to "click here to remove" page has been distributed largely.
In addition to the fact that it sends the user's email address to the spammers it also points to a web page that asks to scroll it. This page uses Drag and Drop vulnerability in Internet Explorer so when the page is scrolled, the exploit runs a proxy backdoor. Currently it downloads and runs windows-update32.exe which is Backdoor.Win32.Agent.ce but since it is controlled by the spammers it could be changed.
The downloaded Agent.CE is a proxy backdoor that runs as service and a normal process. Once installed on the victim's machine, it is intended to serve as a proxy. Such infected host may later be used to relay email and/or spam.
Once detected, the F-Secure security product will automatically disinfect the suspect file by either deleting it or renaming it.
Once the downloaded file is run it copies itself to WINDOWS\SYSTEM32 directory under the name w32.exe. That file attributes are then set to SYSTEM, HIDDEN and READONLY. Then that file is run to perform additional installation steps and to start the normal operation of the proxy.
Agent.CE installation steps include:
* Create a service named "Windows Service Application"
* Alter registry entries to ensure the service starts in Safe Mode and Safe Mode with Networking.
* Alter registry entries to ensure the proxy is started as normal program under system context and later under currently logged user's contex.
After that normal proxy operation mode is entered. In this mode, Agent.CE will listen on TCP port 9687 and a randomly choosen TCP port. That random TCP port number is registered with the controlling web site for further use.
Detection for this malware was published on September 21st, 2004 in the following
F-Secure Anti-Virus updates:
Detection Type: PC