An unusual number of virus attacks succeeded on a large scale in January, according to figures released last week, with an increasing number of viruses managing to wreak havoc before anti-virus vendors could respond.

Israel-based Commtouch, which makes spam and virus protection technology, said there were four "massive attacks" in January, out of 19 new, significant e-mail-borne virus attacks. Eight of these were graded "low intensity" and seven were "medium intensity", the company said.

Speed has always been key to a virus's success, and more attacks are managing to slide in under anti-virus companies' radar, with 40 percent of attacks peaking within eight hours. Speed corresponded to the scale of the attack: on average low-intensity attacks peaked in 27 hours, medium-intensity attacks took 17 hours and the most damaging attacks took as little as 5.5 hours to spread hundreds of millions of emails, according to Commtouch.

On average, the 21 leading anti-virus engines took 8.12 hours to respond to a new attack - though the company didn't say how widely the engines varied from this average. Each engine "missed" an average of 6.2 viruses, meaning the attack had peaked before a signature was available, Commtouch said.

The company, not coincidentally, makes software designed to reduce anti-virus lag time.

One outbreak consisted of seven variants, the first launching around Christmas Day, with subsequent variants growing into a massive outbreak late in January.

The US was the physical origination point for only 43.18 percent of spam around the world in January, down from about 50 percent. China is No. 2, originating 12.89 of spam, with Korea, Germany and France accounting for another 3-4 percent each. Hotmail.com topped the list of domains used as origination points, with others including yahoo.com, msn.com, cisco.com and gmail.com.

Most spam - 52.46 percent - advertised pharmaceutical products, with consumer goods like Rolex imitations making up 14.08 percent, sexual enhancers and diets 13.38 percent.

Finance, software and porn ads made up similar proportions at 7.57 percent, 6.34 percent and a surprisingly low 5.28 percent. Phishing e-mails made up just 0.88 percent of all spam messages.

Commtouch analysed more than 2 billion messages from more than 130 countries to arrive at the figures.