Gaobot.NLL 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:
passwords saved by certain Windows services; keystrokes, in order to obtain information for accessing online banking services, passwords and other confidential information. It affects productivity, preventing tasks from being carried out: - In the affected computer:
it converts the computer into a platform for taking malicious action surreptitiously: spam sending, launch of Denial of Service attacks, malware distribution, etc.
- In the local network:
it generates a large amount of network activity and consumes bandwidth.
It reduces the security level of the computer:
it opens one or more ports to allow remote access to the computer and takes action that compromises user confidentiality; it awaits remote-control orders received through
IRC; it changes system permissions, decreasing the security level. It uses stealth techniques to avoid being detected by the user: - It deletes the original file from which it was run once it is installed on the computer.
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.
- Its code is encrypted and it is only decrypted when it is going to run. Because of this, its code is not legible through a memory dump.
- It terminates its own execution if it detects that a debugging program is active.
Gaobot.NLL 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.
- Via Internet, exploiting remote vulnerabilities: attacking random IP addresses, in which it tries to insert a copy of itself by exploiting one or more vulnerabilities.
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