Websites that automatically download viruses onto users' computers are posing an increased risk to businesses, according to a technology consultant.

These websites are able to install malicious codes onto computers whose internet browsers are not kept up-to-date with security patches, says David Emm, senior technology consultant with security firm Kaspersky.

He explains these 'drive-by downloads' exploit the 'vulnerability' of un-patched browsers, potentially giving hackers access to bank and security details.

'I think because we're using the web more, they're obviously seeing a potential pay-off for them,' Emm claimed.

He says that users are 'not necessarily technically aware' and so 'not aware of the potential dangers'.

To fight the 'bad guys' businesses can set their Windows systems to be automatically updated with security patches by Microsoft every two weeks. Emm recommends installing soft security software which will monitor for worms, viruses and Trojans.

According to Panda Security, common methods used to spread viruses include email attachments promising pictures of naked celebrities; pop-ups pretending to warn of potential problems but actually installing malware and pictures which are actually links to viruses.