The Labour Party has confirmed that details of its members and supporters is among information affected by a “cyber incident” at a company which handles the party’s data.
In a statement sent to all party members on Wednesday, Labour said the “significant” attack was on “‘a third party that handles data on our behalf” and that further inquires are ongoing.
Sources who have been responding to the incident told Sky News the incident was a ransomware attack on the third party supplier.
The matter has been referred by the party to the National Crime Agency (NCA) for investigation.
Labour’s own data systems were unaffected.
“While the party’s investigation remains ongoing, we wanted to make you aware of this incident and the measures which we have taken in response,” the statement from the Labour Party to its members continued.
“We have also provided details of precautionary steps you may consider taking to help protect yourself.”
In a letter to the NCA from Labour, party officials confirm they were informed of the incident on 29 October.
“The third party told us that the incident had resulted in a significant quantity of party data being rendered inaccessible on their systems,” the letter states.
“As soon as the party was notified of these matters, we engaged third-party experts and the incident was immediately reported to the relevant authorities, including the National Crime Agency (NCA), National Cyber Security Centre (NCSC) and the Information Commissioner’s Office (ICO).”
The full scope and impact of the incident is being investigated “on an urgent basis”, a Labour spokesperson said.
Notification emails have been sent to former members and supporters who had left the party.
“We understand that the data includes information provided to the party by its members, registered and affiliated supporters, and other individuals who have provided their information to the party,” the spokesperson added.
The attack appears to be financially motivated and not targeted at the Labour Party itself.
The party urged members and supporters who may have been affected to take extra precautions online, in line with NCSC guidance and to be aware of suspicious emails, phone calls and text messages.
A NCSC spokesman said: “We are aware of this issue and are working with the Labour Party to fully investigate and mitigate any potential impact.
“We would urge anyone who thinks they may have been the victim of a data breach to be especially vigilant against suspicious emails, phone calls or text messages and to follow the steps set out in our data breaches guidance.
“The NCSC is committed to helping organisations manage their cyber security and publishes advice and guidance on the NCSC website.”
The incident isn’t the first time that the party has been impacted by ransomware.
Last year it alerted members that data stored by company Blackbaud had been compromised in a ransomware attack, with names, email addresses, phone numbers, and donation amounts stolen.
At the time, the party said it was believed that information pertaining information about donors over a period of several years had been compromised.