Computer users should protect themselves

Installing anti-virus programs and a firewall is a must, according to Bitkom, a German computer industry association. Users must also download regular updates to ensure those programs can keep worms, trojan horses and spyware at bay.

Not all computer users follow this advice. Around 20 per cent of users have no virus protection program installed, Bitkom says, and around 33 per cent go online without a firewall.

Experts also advise people not to share passwords and access codes with others or leave them unencrypted on a computer. Online computer users should exercise caution with personal data and only share sensitive data via encrypted connections that can be identified by websites that begin with https. Browser windows usually show a small lock icon in encrypted mode.

Damaging programs have been circulating on the Web for 25 years. According to Bitkom, US researcher Fred Cohen created the first computer virus on November 10, 1983.