University students have been bombarded with fake tax refund emails in the last month, HM Revenue and Customs (HMRC) has warned.
It is estimated that hundreds of thousands of students have been targeted in a bid to steal their banking and personal details.
The fraudsters appear to be using .ac.uk email addresses that look genuine, in order to avoid detection.
HMRC said email, text or voicemail would never be used for real refunds.
"Although HMRC is cracking down hard on internet scams, criminals will stop at nothing to steal personal information.
"I'd encourage all students to become phishing-aware - it could save you a lot of money," said financial secretary to the Treasury, Mel Stride.
The tax authority said it was the first time it had seen a tax-scam attack directly targeting university students in such high volumes.
In common with other tax scams, fraudsters send a message - complete with HMRC, Gov.uk, or credit card branding - supposedly telling the recipient about a tax refund.
The recipient's name and email address may be included several times within the email itself.
If tricked, the victim then clicks on a link, into which they enter their banking and personal details.
Fraudsters can use this information to steal money from bank accounts, or to sell on to other con-artists.
Between April and September this year, HMRC requested that 7,500 of these phishing sites be deactivated.
Which universities are being targeted?
Thousands of students have reported cases at certain universities, particularly in the past three or four weeks, but institutions across the country have been targeted.
HMRC said that it was calling on particular universities to raise awareness of the dangers.
They were Aberdeen, Bristol, Cambridge, Durham, Imperial College London, King's College London, Manchester Metropolitan, Newcastle, Nottingham, Plymouth, Queen Mary (London), Queen's (Belfast), Southampton, Sussex, University College London, and Warwick.
It is not known how many students have fallen for the scam or how much they have lost. HMRC believes cases are under-reported.
Pauline Smith, director of Action Fraud, said: "Devious fraudsters will try every trick in the book to convince victims to hand over their personal information, often with devastating consequences.
"It is vital that students spot the signs of fraudulent emails to avoid falling victim by following HMRC's advice."