Shutdowns and disruption of public services are due to rise as the sector finds itself increasingly targeted by distributed-denial-of-service (DDoS) attacks, according to a report by the security vendor Verisign.

Research from the firm indicated that in the last three months of 2014 DDoS strikes, which disrupt services by flooding them with traffic, rose against the public sector more quickly than against any other industry, and now account for 15% of attacks that Verisign respond to.

"Verisign believes the steep increase in the number of DDoS attacks levied at the public sector may be attributed to attackers’ increased use of DDoS attacks as tactics for politically motivated activism, or hacktivism, against various international governing organisations," the firm wrote in the report.

"As outlined in iDefense’s 2015 Cyber Threats and Trends, the convergence of online and physical protest movements contributed to the increased use of DDoS as a tactic against organisations, including the public sector, throughout 2014."

The company added that the increased access to DDoS toolkits online, which can often be downloading from cybercrime forums and websites, and the rise of DDoS services for hire run by groups such as Lizard Squad was likely responsible for the rising attacks.

Such DDoS services can be bought for as little as £1.30 an hour, but prices can run into the thousands of pounds for sustained efforts over several weeks or months.

"In essence, the hiring party is looking for a partner to commit crime with them; deciding which parties are trustworthy and capable is certainly not easy," Verisign said. "To that end, within these forums, a service’s reputation has an enormous impact on its overall success."

Despite the growth in attacks on the public sector, a third of strikes Verisign blocked involved IT services on the cloud, including software-as-a-service (Saas) offerings, whilst a quarter of attacks were still being directed at the media.