More than £190,000 a day is lost in the UK by victims of cyber-crime, police statistics show.
More than a third of victims in that period fell prey to the hacking of social media and email accounts.
Action Fraud said £34.6m was reported to be stolen from victims between April and September 2018, a 24% increase on the previous six months.
The City of London Police, which runs Action Fraud, has warned people to keep separate passwords for online accounts.
The figures show 13,357 people in the UK reported cyber crimes over six months.
More than 5,000 of those people were hacked via their social media and email accounts, costing victims £14.8m.
Commander Karen Baxter said cyber criminals were targeting people's social media accounts "in a bid to make money and steal personal details", adding it could leave victims "at risk of identity theft".
Action Fraud is the reporting centre for people scammed, defrauded or who experienced cyber crime in England, Wales and Northern Ireland.
'We lost nearly £10k to TV licence scammers'
When Jerry Tack received an email saying the TV licence needed paying, he didn't think twice about it.
Nothing seemed suspicious about the website he clicked on, so he entered his bank details - and began a chain of events that would lose him £9,900.
Jerry, from Hampshire, was among thousands contacted in what police called a "particularly nasty" fraud.
But the banks say they cannot reimburse customers who have mistakenly authorised payments to fraudsters.
Commander Baxter said people should "keep a strong, separate password for their email accounts" and use the latest software and app updates.
"Always be suspicious of unsolicited requests for your personal or financial information and never call numbers or follow links provided in unsolicited texts or emails," she said.
Earlier this month Action Fraud reported a "convincing" TV licence email scam had led to more than 5,000 complaints over a three-month period.
Emails with headlines such as "correct your licensing information" would direct users to a fake TV licensing website.
The site then asked victims to provide their payment details, including their account number, sort code, and card verification value (CVV) code on the back of their card.