A new version of a Trojan horse program popular with computer intruders was publicly released on the web Friday, and quickly put to use by an eager underground.
Nearly thirty disguised copies of the newly-released SubSeven 2.2 were already tempting Netizens Monday afternoon, cloaked in filenames promising sexually explicit videos and images, and offered up on Usenet newsgroups that specialize in erotica, experts say.
"That's where the majority of these Trojans are posted," says Patrick Nolan, virus researcher at Network Associates' McAfee AVERT Labs. "This means that the hackers are aggressively promoting their product."
Since its debut in February, 1999, SubSeven has become a favorite tool of intruders targeting Windows machines. While less well-known among outsiders than the mediagenic Cult of the Dead Cow's Back Orifice 2000, SubSeven victims currently outnumber Back Orifice victims by 100-to-1, Nolan estimates, the program's popularity driven by the steady support of its pseudonymous author, "Mobman."
"It has been an evolving Trojan since the early days," says Nolan. "By comparison, Back Orifice is a one hit wonder."
Like other Trojans, SubSeven is divided into two parts: a client program that the attacker runs on his own machine, and a server that he must insinuate into a victim's computer through some subterfuge, usually by misrepresenting it as an image file or an electronic greeting card.
Also like other Trojans, SubSeven can be used as perfectly benign remote administration program, though the official SubSeven web site unabashedly promotes it as an intrusion tool.
Once installed, SubSeven's friendly user-interface allows the attacker to easily monitor a victim's keystrokes, watch a computer's web cam, take screen shots, eavesdrop through the computer's microphone, control the mouse pointer, read and write files, and sniff traffic off the victim's local network.
A SubSeven server can also be programmed to announce itself over ICQ or Internet Relay Chat (IRC), and groups of servers can be remotely controlled as one. That makes the program particularly useful for launching distributed denial of service attacks (DDoS), in which constellations of systems are simultaneously directed to flood a single site with an overwhelming volume of traffic, as happened to Yahoo!, CNN.com, and other online giants in February 2000.
Last October, the FBI's National Infrastructure Protection Center (NIPC) and Internet Security Systems (ISS) warned that another DDoS attack may be imminent, after ISS spotted some 800 machines infected with a SubSeven variant reporting for duty on IRC. The variant was named DEFCON8, for the annual Las Vegas hacker convention, and circulated as SexxxyMovie.mpeg.exe. The anticipated cyber-attack never came.
The new version of SubSeven offers script kiddies increased flexibility in the user interface, a revamped mechanism for customizing the server, and for the first time runs smoothly on Windows NT and Windows 2000. The client is not downward compatible with previous versions of the program, which may slow adoption, Nolan says.
SubSeven 2.2. signatures will likely be quickly be integrated into anti-virus updates. In any event, users who don't accept executables (files ending in the suffix .exe) from strangers are safe from the Trojan.
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