Algiers - Algerian internet users flocked back to social media on Friday following several days of blackout as the government sought to prevent a repeat of leaks of high school test papers.A leak of the papers on social media meant 555 000 out of 800 000 high school leavers who took their final exams at the start of June had to retake them between Sunday and Thursday.Djamila, 45, a sales executive, said she was delighted to be able to connect "normally" at last. Social networks allow her, like many Algerians, to stay in touch with relatives overseas.From Saturday to Thursday, internet-hungry Algerians were blocked from accessing Facebook, Twitter and other social media sites.Fraud in the exams "cannot justify what happened", Ali Kahlane, an expert on information technology and communication, told AFP."This caused the blocking of a whole country," he said.Many tech-savvy Algerians were able to get around the block, connecting via VPN - a type of "secure tunnel" in the internet that allows users to appear to be connecting from a different country. As well as the social media block, internet access in general was slow and faced interruptions. The government denied having disrupted the country's entire internet service.But the cuts also hurt businesses. Hassen Khelifati, chief of an insurance company, said he had lost 50% of his turnover for the week due to difficulties getting online."The problem is the surprise. We weren't prepared for the internet to be cut. The two first days, there was a total blackout," he said.Algeria has around 20 million internet users including 16 million who use mobile services. Sharing of messages, photos and video has become wildly popular since the launch of 3G services in 2013.