Grum.F is a worm that spreads by copying itself, without infecting other files.
It captures certain information entered or saved by the user, with the corresponding threat to privacy:
It sends the gathered information to a remote user by any available means: email, FTP, etc.
- On remote sites: it mass mails junk mail (spam).
It reduces the security level of the computer:
it changes the security settings of Internet Explorer, decreasing its security level; it awaits remote-control orders received through
HTTP; it changes system permissions, decreasing the security level.
It uses stealth techniques to avoid being detected by the user:
- It uses techniques included in its code to hide itself while it is active.
- It modifies system permissions in order to hide itself.
It uses several methods in order to avoid detection by antivirus companies:
- It terminates its own execution if it detects that it is being executed in a virtual machine environment, such as VMWare or VirtualPC.
- It terminates its own execution if it detects that a debugging program is active.
Grum.F uses the following propagation or distribution methods:
- Exploiting vulnerabilities with the intervention of the user: exploiting vulnerabilities in file formats or applications. To exploit them successfully it needs the intervention of the user: opening files, viewing malicious web pages, reading emails, etc.
- File infection: it infects different types of files, which are then distributed through any of the usual means: floppy disks, email messages with attachments, Internet download, files transferred via FTP, IRC channels, P2P file sharing networks, etc.