IT systems at NUI Galway remain offline, after an attempted cyberattack was detected earlier today.
All internet traffic into and out of the university has been blocked, as tech specialists investigate the issue.
Connections with satellite sites operated by the university in Connemara and Donegal are also down.
The shutdown has impacted students hoping to access course material or lectures remotely.
Security checks are under way in an effort to see if any data breaches have occurred.
The university says, at this stage, there is no evidence to suggest material has been compromised.
Staff and students were initially informed of a "disruption to connectivity" before 9 o'clock this morning.
A subsequent email informed them that there had been an attempted cyberattack.
Access to university cloud-based platforms including email, MS Teams and Zoom remains possible from off-campus locations.