The UK's national security adviser Sir Peter Ricketts has warned that government websites could become the next target for pro-Wikileaks hackers.
He told civil servants that websites used to file tax returns or claim benefits could be the most vulnerable.
So far attacks from the Anonymous group of hacktivists have concentrated on firms perceived to be anti-Wikileaks.
Wikileaks founder Julian Assange has been granted bail by a London court.
A spokesperson for the Prime Minister told a press briefing that Sir Peter had spoken to permanent secretaries about the security of government websites in the light of pro-Wikileaks attacks.
"The priority would be websites that dealt with information that belonged to members of the public such as the DWP [Department for Work and Pensions] and HMRC [Revenues and Customs], he said.
The government did not want to speculate on the scale of the problem.
UK web attacks could be likely because Mr Assange has appeared in court.
He has been granted bail but will remain in prison pending an appeal against the decision. He is wanted by authorities in Sweden for questioning over two sex crimes.
He denies the crimes and will fight extradition, his lawyer said.
His mother Christine Assange, who has visited him in prison, said he remained committed to the ideals of Wikileaks.
She also passed on his thoughts on the firms which have withdrawn services from the whistle-blowing site.
"We now know that Visa, Mastercard, PayPal and others are instruments of US foreign policy. It's not something we knew before," Mr Assange said.
The US government has denied that it wrote to individual firms, asking them to stop doing business with Wikileaks.
To date, members of Anonymous - a loose-knit group of net campaigners - have focused their distributed denial-of-service attacks on these firms rather than governments.
The attacks, which flood websites with so much traffic that they fall over, have had some success.
Both Mastercard and Visa, which have stopped processing payments to the Wikileaks site, experienced web outages last week.
The attacks are co-ordinated via an online tool which members of Anonymous are being encouraged to download.
The tool, which volunteers people's computers to become part of the attack, has now been downloaded more than 80,000 times.
The attacks are a protest against attempts to close down Wikileaks and end the publication of 250,000 secret US diplomatic cables.
Some have described the fight between Anonymous, Wikileaks and the US government as the "first infowar".
But security experts have downplayed the conflict.
"It was a demonstration, a protest, nothing more than political theatre - entertaining and influential but not war," James Lewis, a specialist in cybersecurity at the Washington think-tank the Centre for International and Strategic Studies, CSIS, told BBC News.
Allan Friedman, a research director at the US Brookings Institution's technology innovation centre, agreed.
"It's very much not a cyberwar. If we are calling it war, we are devaluing what war is. It's a cyber mob.
"Mobs can be destructive but they tend not to have a long lasting impact."
Some members of Anonymous are also keen to distance themselves from the attacks.
"Many of us are law-abiding citizens of our respective countries around the world," Anonymous member Phill Midwinter told BBC News.
"We're currently involved in more forward-thinking projects that help to spread our message of internet transparency in a more open and productive manner," he added.
This includes a new venture dubbed Operation Leakspin, which aims to release details from the leaked cables that the mainstream media has overlooked and summarise them "into chunks that everyone can understand".
Meanwhile the US government remains determined to bring Mr Assange and Wikileaks to book.
It is exploring a nearly century-old spy law as a way to prosecute Mr Assange.