Microsoft has warned users of Internet Explorer, the world’s most popular web browser, that a newly discovered flaw in the programme could let hackers take control of their computers.

Users can infect their computers by visiting a malicious website or reading an infected e-mail. They don’t have to open an attachment or download a program.

The problem, which a affects graphics code called Vector Markup Language, was discovered by the American company Sunbelt Security.

Researchers at the company found pornographic websites that were exploiting the vulnerability to install programmes known as spyware, which can harvest personal details such as banking passwords and credit card numbers from affected computers.

Hackers could also take control of a computer and use it to send out spam e-mails or to mount attacks on other websites. Users may be unaware of the intruder within their PC, although affected machines will usually run more slowly than usual and may crash unexpectedly.

Microsoft recommended that users of Internet Explorer should not click links in unsolicited e-mails and should avoid logging on to their PCs with administrator rights for day-to-day computing.

"An attacker who successfully exploited this vulnerability could gain the same user rights as the local user," it said "Users whose accounts are configured to have fewer user rights on the system could be less impacted than users who operate with administrative user rights."

Microsoft has said that it is working on a patch to correct the problem, but warned that it may not be ready until October 10.

The anti-virus company Sophos warned that conventional security programs would not protect PCs from the vulnerability. "Anti-virus and firewall will not help in this instance," Carole Theriault, a senior security consultant at the company, said.

"Until a patch is available, we would advise users not to use Internet Explorer, and to configure their e-mail client to view e-mails in plain text only," she said.

Explore Tech & Web

• Personal Tech

• The Web

• Gadgets & Gaming