At first sight it looks like a lot of nonsense; in fact, the latest list of the most popular email header terms show that spammers are becoming increasing sophisticated in their efforts to attract users to their emails.

According to email filtering vendor Roaring Penguin Software, the most common header contained in spam emails for August 2005 was ‘ffffd5’ – HTML code for a pale yellow colour.

Other popular terms included the names of various impotency related drugs. Also popular was the term ‘B0000AZJVC’, which could possibly be a coupon code, or ‘randomly’ generated code intended to make it more difficult for Bayesian filters to identify messages as spam.

The inclusion of HTML style attributes probably indicates that “spammers must be using Web authoring software to make their e-mail pretty,” says David Skoll, of Roaring Pengiun.

With spam now accounting for the majority of email traffic, efforts to combat it are intensifying. Analysts at IDC recently forecast that worldwide spending on anti-spam products will exceed $1.7 billion in 2008, a massive increase from the $300 million spent in 2003.

“Whether the next several years will show continued improvements in effectiveness, accuracy, and reducing the costs of spam will depend on how quickly and well anti-spam solutions keep up with the latest spam innovations and are deployed and managed with antivirus as core elements of broader network security solutions,” said Brian Burke, research manager at IDC.

According to Roaring Penguin, the following words have the dubious honour of being the most likely to indicate a spam email in August 2005:

1. ffffd5
2. Wavefrt
3. Cialis
4. Tadalafil
5. edit1
6. go-button-software
7. display-variation
8. eyebrow-upper-left-corner
9. B0000AZJVC
10. right-topnav-default-2