Town Hall number-crunchers say a cyber attack in October 2020 cost the council £12.2m in the last financial year.
This includes more than £444,000 spent on IT consultancy, £152,000 on recovery of the Mosaic systems used for social care data, and £572,000 on the housing register in the last financial year.
The figures were disclosed to the Citizen during the annual inspection of council accounts.
The Town Hall spent millions on specific cyber recovery work and replacing systems affected by the hackers, who struck two years ago this week – as staff were working to support residents through the pandemic.
The National Crime Agency (NCA) is still investigating the attack.
In January 2021, those responsible for the hack said they had published some of the data on the dark web.
Hackney Council said it has never paid ransom and never would.
It has stated that “the vast majority of the sensitive or personal information held by the council is unaffected”.
The hack wreaked havoc across the council’s services, causing delays with benefits claims, adding people to the housing register, and land registry searches.
Staff had to record data on paper when the computer systems were compromised.
In January this year, neighbourhoods and housing group director Ajman Ali told councillors: “You probably won’t believe when I say that staff had actually gone to pen and paper. I’ve been down in the council, down at the depot – piles and piles of A4 paper on staff desks, actually putting down job tickets and waiting to put them down onto the computer system.”
His colleague Steve Waddington said the hack saw data lost for “a high number” of people whose benefits were processed between July and October 2020.
The attack even caused problems with printers used by the public in the borough’s libraries.
The NCA has not responded to a request for an update into its investigation.
It is believed the hackers are based overseas and have not been charged.
Hackney Council said its recovery effort has included clearing a backlog of land searches for property transactions, processing business rates and council tax more rapidly, and dealing with Covid support grants and council tax energy rebates “within the timescales set out by the government for those schemes”.
It said it was also processing all new claims for housing benefits and “the vast majority of changes of circumstances have also been processed”. They expect to deal with these in “normal timescales” by the end of the year.
The council is also aiming to update the systems to add applications to join the housing register and changes of circumstances by the end of 2022.
The Housing Ombudsman criticised the Town Hall for delays in dealing with a resident’s application in 2020, despite acknowledging “the unique challenges imposed by the cyber attack”.
A council spokeswoman said: “We are sorry for the impact that this serious criminal attack has had on our residents. Council staff have done everything possible to minimise impacts and return services to normal as quickly as possible.
“We are extremely grateful for their tireless efforts and to our residents for their continued patience.”