One in 20 UK internet users say they have lost money through online scams, research into spam emails suggests.
Online frauds are becoming more sophisticated
Almost half say they have received so-called phishing emails aimed at tricking them into revealing details like online banking passwords.
Other frauds include paying for items which never arrive and sending cash following a demand from a bogus email.
Of the 1% who had lost money through phishing, 53% were not compensated by their bank, the AOL survey found.
A further 11% say they are still waiting for compensation.
Phishing emails are becoming more sophisticated and often direct users to bogus websites replicating legitimate brands.
A quarter of respondents were not aware that they could be held liable even if they unwittingly provide information to an online fraudster.
AOL said many UK banks are currently compensating losses incurred as the result of phishing but this might change in future.
Online frauds often totalled less than £100 ($190) which might make it easier for criminals to carry on undetected as such amounts may be overlooked, it added.
"As well as using spam filters and being wary of unsolicited emails, we would advise internet users to check their bank balance regularly and read their bank's terms and conditions," said Will Smith, AOL's safety and security expert.
The YouGov poll of 2,052 internet users for AOL took place between 22 and 25 April.