Questões de Concurso

January 23, 2009
Worm Infects Millions of Computers Worldwide
By JOHN MARKOFF

    A new digital plague has hit the Internet, infecting millions of personal and business computers in what seems to be the first step of a multistage attack. The world’s leading computer security experts do not yet know who programmed the infection, or what the next stage will be.
    In recent weeks a worm, a malicious software program, has swept through corporate, educational and public computer networks around the world. Known as Conficker or Downandup, it is spread by a recently discovered Microsoft Windows vulnerability, by guessing network passwords and by hand-carried consumer gadgets like USB keys.
    Experts say it is the K1K1 infection since the Slammer worm exploded through the Internet in January 2003, and it may have infected as many as nine million personal computers around the world.
    Worms like Conficker not only ricochet around the Internet at lightning speed, they harness infected computers into unified systems called botnets, which can then accept programming instructions from their clandestine masters.
    Many computer users may not notice that their machines have been infected, and computer security researchers said they were waiting for the instructions to materialize, to determine what impact the botnet will have on PC users. It might operate in the background, using the infected computer to send spam or infect other computers, or it might steal the PC user’s personal information.
    Microsoft rushed an emergency patch to defend the Windows operating systems against this vulnerability in October, yet the worm has continued to spread even as the level of warnings has grown in recent weeks.
    Earlier this week, security researchers at Qualys, a Silicon Valley security firm, estimated that about 30 percent of Windows-based computers attached to the Internet remain vulnerable to infection because they have not been updated with the patch, despite the fact that it was made available in October.
    Unraveling the program has been particularly challenging because it comes with encryption mechanisms that hide its internal workings from those seeking to disable it.
    The program uses an elaborate shell-game-style technique to permit someone to command it remotely. Each day it generates a new list of 250 domain names. Instructions from any one of these domain names would be obeyed. To control the botnet, an attacker would need only to register a single domain to send instructions to the botnet globally, greatly complicating the task of law enforcement and security companies trying to intervene and block the activation of the botnet.
    Several computer security firms said that although Conficker appeared to have been written from scratch, it had parallels to the work of a suspected Eastern European criminal gang that has profited by sending programs known as “scareware” to personal computers that seem to warn users of an infection and ask for credit card numbers to pay for bogus antivirus software that actually further infects their computer.
    One intriguing clue left by the malware authors is that the first version of the program checked to see if the computer had a Ukrainian keyboard layout. If it found it had such a keyboard, it would not infect the machine, according to Phillip Porras, a security investigator at SRI International who has disassembled the program to determine how it functioned.

(Adapted from The New York Times)