Image spam and spam touting sexual enhancement drugs are both increasing in frequency, according to the security software firm BitDefender.

This kind of spam in increasing so much that it is actually getting more common than pump-and-dump spam.

Most of the image spam being sent is related to penny stocks, BitDefender stated, while those touting drugs were more likely to be text.

Vlad Valceanu, the chief of BitDefender's Antispam Laboratory, said: "Spammers are emailing fewer targets at a time, while introducing small variations in every email in the hope of avoiding timely detection.

"We expect to see more of this in the next half of the year, as well as increased use of attachments and possibly even embedded Flash."

Spam with ZIP and PDF files attached are also becoming increasingly common, according to BitDefender.

Meanwhile, Microsoft has just released its second largest bundle of patches this year.