A 'significant proportion' of IT directors are unaware of the newest email threats, according to a new report.

A survey conducted for instant messaging firm TumbleWeed claims that one in five IT heads does not know if their firm has been the victim of malicious email traffic.

David Carey, technical director at Tumbleweed says spammers and online fraudsters can bring down a network with a Denial of Service (DoS) attack or gain access to confidential files through a Directory Harvest Attack (DHA).

'Our study revealed an alarming proportion of IT directors are completely unaware of whether they have been attacked by a DoS or DHA in the last year,' he said.

A DoS attack is essentially an attempt to overwhelm the servers of a company by bombarding them with vast volumes of inbound traffic.

The DHA, on the other hand, is a computerised attempt to identify valid email addresses in preparation for spamming. Emails are sent out to random addresses, and those that do not return rejection emails are used in future spamming attacks.

Other results from the survey indicated that 17 per cent of companies have been hit with DoS attacks in the past year alone, with large retail based firms most likely to be attacked.