Warnings have been issued to staff at the Northern Ireland Assembly after cyber attacks on the IT system.
It's understood the attacks on the email system came from an external source, with attempts to access mailboxes using numerous passwords.
A guidance email sent to staff seen by the Belfast Telegraph said the Assembly IT office was working closely with Microsoft and the National Cyber Security Centre to address the issue.
An Assembly spokesman said: "The Assembly Commission's IT system has been subjected to unauthorised attempts to access email accounts. We are taking all necessary steps to manage and mitigate this and are working with the appropriate authorities, both locally and nationally.
"The Assembly takes the security of its IT systems very seriously and strives continually to ensure that all systems are secure.
"The Commission does not wish to comment any further at this stage."
The bid to breach security follows a report last month that UK councils had been targeted by nearly 100 million cyber attacks in five years, with 25 councils experiencing data losses.
The organisation Big Brother Watch said this meant criminals were bombarding councils at a rate of 37 times a minute, putting the personal data of millions of residents at risk.
This month the UK's Joint Forces Command and the United States National Security Agency held strategic talks on how to counter the growing online threat.
The recent guidance issued by the Assembly urged staff to review and change their current passwords.
Weak password types like 'password123' were to be completely avoided, as well as dictionary words combined with numbers, like 'Spring2018'. The safest option is said to be three unrelated words like 'CoffeeTrainFish', but should also include at least one capital and numerical character.
Easy to guess combinations like 'onetwothree' or the names of family and pets are also discouraged.
Workers were reminded to update their passwords on all other devices like laptops and mobile phones.