Computer hackers seeking financial gain rather than thrills or notoriety are increasingly flooding the Internet with malicious software code, according to a semi-annual report issued on Sunday.
Symantec Corp.'s Internet Security Threat Report said during the first half of 2005 the number of new viruses targeting Microsoft Windows users jumped 48 percent to nearly 11,000 compared to the previous six months as hackers used new tools and a growing sophistication to create malicious code.
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The latest report by the world's biggest security software maker also found that viruses exposing confidential information made up three-quarters of the top 50 viruses, worms and Trojans, up from 54 percent in the last six months of 2004.
It also said an increasing amount of menacing software allowed spam to be relayed automatically from computer to computer. These so-called "Trojan" programs can download and install adware to display pop-up ads in a user's Web browser.
More so-called robot, or "bot" networks, which are created when a hacker illegally gains control of a large number of computers, are now available for sale or rent in the underworld of the Internet, Symantec said.
"As financial rewards increase, attackers will likely develop more sophisticated and stealthier malicious code that will attempt to disable antivirus, firewalls, and other security concerns," the report said.
Vincent Weafer, a security expert at Symantec, said early generations of cybervandals tended to unleash viruses as a way to bolster their reputations in the murky hacker world but now the motivation has turned to financial gain using more targeted malicious software.
The number of headline-grabbing viruses has slowed since the Blaster worm outbreak in 2003, which targeted Microsoft software and devastated hundreds of thousands of computers worldwide.
Instead, there is now a surge in people trying to gain control over a network of computers to launch attacks as well as a growing number of phishing scams that trick users into clicking onto a Website that contains infected code, he said.
"We are seeing a very significant change where we are seeing far fewer large pandemics," Weafer said. "However we are seeing a large volume increase in cyberattacks, viruses and variants."
Indeed, Symantec saw an average of 10,532 active bot network computers per day, an increase of more than 140 percent over the prior six months.
It also said phishing messages grew to an average 5.70 million messages a day from 2.99 million. "What we are saying is that attackers are increasingly targeting your assets and your private information," Weafer said.