Darkmail: Cyber nasties just got nastier

The number of phishing emails sent to UK businesses increased by 45 per cent in July, according to the latest figures from email security company BlackSpider Technologies.

Phishing is not the only kind of email-based attack causing concern. Email management firm Email Systems also reports that over the last 12 months it has registered a 400 per cent rise in 'darkmail'.

Darkmail is speculatively targeted, unsolicited mail, and its rise threatens the efficiency of UK computer systems as well as their security. In one type of attack, a domain is targeted and then deluged with randomly addressed emails. Those not bounced back by the mail server are taken to be 'live' addresses that can then be attacked in other ways.

Darkmail is a relatively new phenomenon, and Email Systems says it has risen in prominence recently because of "a significant increase in the frequency of email attacks that target a specific domain", including DDoS attacks and directory harvest attacks (DHA). Even darkmails that are never received "have the potential to sap a huge percentage of network bandwidth", the company said.

One unnamed Email Systems client in the manufacturing sector with less than 10 employees was recently targeted with more than 10 million emails in a single day. Neil Hammerton, chief executive of Email Systems, said in a statement: "Our statistics show that over the last 12 months, spam attackers are becoming increasingly speculative in their approach to reaching an actual user."

This underlines BlackSpider's survey, which reported that the company had detected more than 360,000 emails carrying a phishing threat in July, compared to just less than 250,000 in June.

BlackSpider's monthly statistical analysis also revealed the new viruses released in July included six variants of the Win32.small Trojan downloader. The top five in July in descending order were: W32.Netsky.P, Phish-BankFraud.eml.b, W32.Mytob.DF, W32.Mytob.EE and W32.Mytob.ED.

Spam levels reached a yearly high in July, accounting for 77 per cent of all email sent but virus-laden emails dropped slightly from 2.9 per cent in June to 2.6 per cent in July.

Colin Barker writes for ZDNet UK