Security firm SoftScan claims that its anti-spam systems identified 90.3 per cent of email as junk during February, the highest average it has ever recorded.
After sudden dips in spam levels at the beginning of the year, February showed that spammers are still out there in force, the company said.
The highest levels were seen at the weekends when there is less legitimate email. On one Sunday in February spam reached a record 96.22 per cent.
November 2006 was the last time that spam levels were as high when they reached 89.73 per cent.
"Even on a good day when spam levels are comparatively low the overall trend is creeping upwards, which is not good news for email users," said Phil Watts, managing director of SoftScan UK.
"Without harsher sentencing and greater fines, there is little incentive for the majority of spammers to cease."
Watts explained that, while their have been some notable convictions recently, including those of Jeffrey Goodin and Joshua Eveloff, the perceived risk for the financial gain is very low.
"Like the botnets the spammers control, even when one disappears a replacement is always available," he said.
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