OTTAWA - The Canada Revenue Agency has resumed all online services after fraudsters used thousands of pilfered usernames and passwords to obtain government services.

The agency disabled the services Saturday after discovering more than 5,000 accounts had been the target of three cyberattacks.

Online access to "My Business Account" resumed Monday and all others were brought back online Wednesday evening.

The agency says it regrets the impacts on Canadians and has modified all its security systems to protect against future cyberattacks.

All individuals affected by the cybersecurity breaches will receive a letter from the CRA explaining how to confirm their identity in order to protect and restore access to their account.

The agency urges everyone using its online services to update their accounts with unique passwords they don't use for any other purpose.