Trojan horses disguised as recruitment letters are the latest threat that senior employees at major firms are having to deal with, according to MessageLabs.

The security firm told News.com that no fewer than 1,100 emails containing malware -infected rich text files - were sent between September 13th and 14th this year, highlighting the need for firms to have robust IT support in place.

"All [the emails] were going after management. The emails included the company name in the subject field, purporting to be a recruitment company," a spokesperson for MessageLabs said.

"What it had in the attachment is an executable RTF [rich text] file."

As well as this, the emails were addressed to just one recipient, making them look more legitimate. When they were activated, these files opened up a connection between the recipient's computer and the hacker's server.

The MessageLabs spokesman said that this kind of email poses a large threat because of their top-down nature. Anyone would be inclined to open an email that seemed to be sent by their bosses, and if they were forwarded within an organisation they would be coming from a trusted source.

In a recent survey of SMEs for Connect, the two most important benefits of outsourcing were 'guaranteed response times' and 'allowing in-house IT staff to concentrate on more strategic issues'