A Lancashire university is among three UK institutions to be hit by cyber-attacks in the last week.
University of Central Lancashire in Preston said Sunday's incident had left remote-working students unable to submit assignments.
The University of the Highlands and Islands in Scotland and Queen's University in Belfast were also targeted.
The National Cyber Security Centre has launched an investigation.
The government organisation, a division of GCHQ, said it could not confirm if the attacks were linked.
A UCLAN spokesman said the attack on Sunday was "rectified within hours" and Lancashire Police were informed.
The force has been asked to comment.
'Period of downtime'
The spokesman said UCLAN had "deployed a full incident response plan to evaluate the extent of the issue and to stabilise the situation" and no data was lost.
He said the university suspended access to a number of its systems as a precautionary measure, meaning "a short period of downtime" for students and staff.
"Our core student learning systems were largely back to full operation on Sunday evening, meaning that teaching and learning could continue on Monday," he added.
On Friday Queen's University in Belfast had to suspend access to systems as a precaution following a similar attack.
And on Monday sites belonging to the University of the Highlands and Islands in Scotland were targeted.
A spokesman for The National Cyber Security Centre said it was working with the universities in the aftermath of the incidents.
He said universities had been reminded on the dangers of cyber-crime in a special report from the organisation in 2019.