February 23, 2011

Zombie Computers.

Zombie computers.

   Zombie computers are computers that have been taken over by a hacker without the knowledge of the owner.

A computer hacker who intends mischief or harm, secretly infiltrates an unsuspecting victim's computer and uses it to conduct illegal activities. The user generally remains unaware that his computer has been taken over  he can still use it, though it might slow down considerably. As his computer begins to either send out massive amounts of spam or attack Web pages, he becomes the focal point for any investigations involving his computer's suspicious activities. 

 The user might find that his Internet Service Provider (ISP) has canceled his service, or even that he's under investigation for criminal activity. Meanwhile, the cracker shrugs off the loss of one of his zombies because he has more. One investigation allegedly discovered that a cracker's single computer controlled a network of more than 1.5 million computers

Crackers transform computers into zombies by using small­ programs that exploit weaknesses in a computer's operating system (OS). In order to infect a computer, the cracker must first get the installation program to the victim. Crackers can do this through e-mail, peer-to-peer networks or even on a regular Web site.

 Most of the time, crackers disguise the malicious program with a name and file extension so that the victim thinks he's getting something entirely different.
Once the victim receives the program, he has to activate it. In most cases, the user thinks the program is something else. It might appear to be a picture file or some other recognizable file format. When the user chooses to run the program, nothing seems to happen. For some people, this raises alarm bells and they immediately follow up with a flurry of virus and spyware scanner activity. Unfortunately, some users simply think they received a bad file and leave it at that.

Meanwhile, the activated program attaches itself to an element of the user's operating system so that every time the user turns on his computer, the program becomes active.
Once a user's computer is compromised, the cracker pretty much has free reign to do whatever he likes. Most crackers try to stay below the radar of users' awareness. For some crackers, this isn't much of a problem since some networks number in the hundreds of thousands of zombies..
Preventing Zombie Computer Attacks.

  • Antivirus software is an absolute necessity. 
  •  Install a firewall to protect your home network.
  •  You should also make sure that your passwords are difficult or impossible to guess.
  • Delete SPAM  mails, without opening them.
  • Don't open unknown or free games or applications.


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Besides relaying spam and launching DOS attacks, a zombie machine can be used to send phisher scams, spread viruses, download pornography, and steal personal information, says Carole Theriault, a Sophos security consultant.

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