Students at Oxford University are being warned that university authorities are using the Facebook website to gain evidence about unruly post-exam pranks.
Students at Oxford are celebrating the end of exams
The student union has urged students to tighten their security settings on the social networking website, to stop dons viewing their details.
The union said, while it did not condone anti-social behaviour, the privacy of students was paramount.
But the university said there had been complaints about students' behaviour.
On its website, the Oxford University Student Union warns: "We advise those of you with Facebook accounts to alter your privacy settings on Facebook to prohibit members of staff and faculty from viewing your profile and photographs.
"While the Student Union does not condone unruly, violent or disorderly behaviour, we believe that the privacy of our members should be protected and that disciplinary procedures at all levels within the university should be fair and transparent."
President of the Oxford University Students Union, Martin McCluskey, has also e-mailed members to warn that their online community is being spied on.
"It has been brought to the attention of the Student Union that the proctors have been using evidence gathered from Facebook for disciplinary matters," he warns.
"Specifically, photos from post-exam celebrations on Merton Street have been sent to members of the university (including those already finished) as evidence of their being involved in 'trashings'."
A spokesperson for Oxford University said university proctors - senior academic staff who deal with disciplinary matters - were looking at public pages on Facebook that were accessible to all members on the Oxford network.
"There's no subterfuge of pretending to be someone you aren't," the spokesman said.
"The university proctors have told the students that they are welcome to meet their friends after their exams but that students who create a mess in the street with food or alcohol, or who indulge in anti-social behaviour contrary to university regulations will be disciplined," he said.
"Over recent weeks the university proctors have received numerous complaints from university staff and members of the public about a significant minority of students taking part in anti-social behaviour that seriously affected those who live and work in the city of Oxford.
"Given these concerns, the proctors wish to take the steps available to them to identify and discipline the culprits."