In the widespread scam, companies are sent notices from bogus government agencies demanding up to £135 to register their business under the Data Protection Act.
Previously, the scam had been targeting a wide range of businesses, but evidence gathered by the Information Commissioner's Office suggests that software and IT companies have now become the fraudsters' primary targets.
The letters, which request sums of between £95 and £135 to register under the Data Protection Act, often use threatening language and official-looking headed paper to con businesses.
Information commissioner Richard Thomas warned companies not to be duped by these bogus agencies.
"The golden rule is that if you receive a letter out of the blue demanding more than £35 to register under the Data Protection Act, this will be a scam," he said. "Our simple message to businesses is to throw the letter in the bin and not to pay the fee demanded."
Guidance on compliance