The time that an unpatched PC can survive connected to the Internet has dropped to an average of 20 minutes, down from 40 minutes in 2003.
According to the latest data from the Internet Storm Center at the US-based SANS Institute, which provides research and education on security issues, the historical trend is continuing its downward journey, and has now reached a point at which it does not provide enough time to download the very patches that would protect a system from malware.
SANS calculated the survival time of a PC using the average time between probes of an average target IP address from worms attempting to propagate for an average target IP address.
"If you are assuming that most of these reports are generated by worms that attempt to propagate, an unpatched system would be infected by such a probe," said the Institute in a statement. However, it said, the result is only an average, and times will vary widely from network to network.
"Some of our submitters subscribe to ISPs which block ports commonly used by worms," said the Institute.
"As a result, these submitters report a much longer 'survival time'. On the other hand, university networks and users of high speed Internet services are frequently targeted with additional scans from malware like bots. If you are connected to such a network, your 'survival time' will be much smaller."
The main issue, said SANS, is that the time to download critical patches now commonly exceeds this survival time. Part of the problem, say security experts, is IT's reliance on patch management..
Speaking at the recent Microsoft TechEd developer conference in Amsterdam, Microsoft Security consultant Fred Baumhardt said the day is likely to come when a virus or worm brings down everything.
"Nobody will have time to detect it. Nobody will have time to issue patches or virus definitions and get them out there. This shows that patch management is not the be all and end all."
Baumhardt drew an analogy with the human body catching the 'flu. "Imagine if your body said 'Hmm, I have the flu, I’ve never had this before, so I‘ll die.' But that doesn't happen: your body raises its temperature and so on, to buy time while other mechanisms kick in."
"If the human body did patch management the way IT does we’d all be dead."