Zombie PCs spreading spam

, an e-mail security company, today reported that 56 percent of all spam filtered by the company in July 2005 originated from computers hijacked by Trojan horses. These Trojan horses typically reside on high-speed, always-on, DSL-enabled computers with outdated or no antivirus or firewall protection, allowing criminal hackers remote access 24/7 to a compromisd PC. Networks of these compromised or "zombie" PCs are being used as spam relays because they hide the true sender. MX Logix reports that in June 2005 zombie PCs accounted for 65 percent of all spam and in May 2005 the number was 55 percent.