The latest Department of Trade and Industry report into the security practices of UK businesses has shown that companies are patching their systems more frequently and seeing benefits from the results.

In 2005 nearly nine out of 10 of UK companies installed security updates within a week of issue, up from 79 per cent in 2004.

Companies that installed critical patches within 24 hours suffered fewer virus infections than those that waited a week.

"It is very encouraging to see the progress that UK companies have made in installing antivirus software and patching their systems," said Chris Potter, a partner at PricewaterhouseCoopers LLP, who is leading the survey.

"The threat has never been greater, so this is no time for complacency. A multi-layer defence of patching, up-to-date antivirus software and intrusion detection software offers the best protection."

But while the vast majority of companies now have antivirus protection, a fifth of those surveyed do not update their virus signature files on a daily basis. Some virus infections are taking up to 50 days to clear up.

The survey also found that companies without antivirus protection are not reporting many incidents, but the report suggested that this may be because they do not realise they have been infected.

The survey was conducted between October 2005 and January 2006 and was based on 1,000 telephone interviews with organisations of all sizes across the UK.

A series of face-to-face interviews with information security officers supplemented the telephone interviews.