Image spammers use non-registration websites to their advantage

Spammers are now hosting images on sites that do not require registration, then linking to those sites from the bodies of spam emails — instead of embedding messages within the emails themselves, according to the report.

The level of total spam captured during May decreased from the month before, dropping 3.4 per cent to 72.7 per cent of all email, according to MessageLabs.

Paul Wood, senior analyst at MessageLabs, told SCMagazine.com today that image spam is difficult to measure because it increases sharply over short periods of time.

"What we’ve been seeing is that it’s quite a difficult metric to capture. It varies depending on when you take the measurement. A lot of image spam will go out in text form, as well as with an image, so depending on when you take the measurement, you can get quite different results," he said.

"Over a longer period, it tends to flatten out a bit. Over the last couple of months, it’s been higher, but I wouldn’t say that it’s been massively high, as we’ve seen in some reports."

Image spam levels have fluctuated widely in recent months, according to reports from various sources.

A report on April’s email-borne threats from Symantec showed a 10 per cent drop in image spam from March to April, when it accounted for 27 per cent of all spam.

McAfee last month reported a drastic drop in image spam, with Nick Kelly posting on the McAfee Avert Labs Blog that emails using the technique plummeted from 59 per cent of all spam at the start of April to 12 per cent near the end.

Last month, researchers at Fortinet said they had seen an April increase in image spam, but those statistics were still dwarfed by those from earlier this year.

MessageLabs’ latest email security report also noted an increase in "spam surges," the practice of targeting individual domains in one aggressive spam attack.

The New York-based vendor noted that one attack lasted 11 hours and sent 10,000 spam messages.

Phishing attacks rose by 0.4 per cent during May, accounting for one in 156.3 emails, or 79 per cent of all malicious email traffic.

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