Pornographic spam levels continue to drop and reached an all time low in February, according to new research by Symantec.

The report shows that of all the spam emails intercepted by Symantec last month, only three per cent could be classified as adult material. This includes pornography, personal adverts and relationship advice, as well as any other messages containing or referring to products or services intended for people over the age of 18.

Unwanted emails offering and advertising health-related products came out joint top with spam presenting general goods and services (24 per cent each). Of all the spam email traffic, 21 per cent related to financial products, 15 per cent offered internet services and three per cent were phishing scams, according to Symantec.

The monthly report also found that attackers are combining slanted text with other image spam obfuscation techniques to avoid detection by spam filters. Rather than making changes to individual characters within the text of the image, the text is slanted at either an upward or downward angle to evade blockage in anti-spam technology that relies heavily upon optical character recognition (OCR) or edge detection, the report said.