Sports fans are being urged to be aware of the risk of scams that could take advantage of people's disappointment at missing out on Olympics tickets.
Some will be unable to secure tickets, even following the second wave of sales.
Trading standards officers fear that some fake websites will be set up promising to supply tickets.
Websites that take people's money and disappear have been set up prior to other major events and festivals.
About 1.8 million people applied for 20 million tickets, but only 6.6 million tickets were available for the London 2012 Games.
Only approved resellers are allowed to sell the tickets, all of which are listed on the official London 2012 website.
A website checker is also in place to help people cross-reference whether the website is legitimate.
Other tips for major sporting events in general include checking contact details and terms and conditions before applying for tickets online and being suspicious of tickets sold in bulk and temporary websites.
Nicola Schofield, team manager at Nottinghamshire Trading Standards, said they were expecting some issues in the run-up to the Games.
"People should keep to genuine sources of tickets, otherwise tickets might fail to turn up or people may be denied entry," she said.
Ahead of the last Olympics in Beijing, the parents of gold medallist swimmer Rebecca Adlington, who is from Mansfield in Nottinghamshire, spent nearly £1,100 on tickets they ordered from a website, which turned out to be a scam.
Any tickets unsold by organisers for the 2012 Olympics will be made available in further ballots, along with the possibility of additional tickets for higher-profile events being released as venues are tested and capacities finalised.
Ebay, the internet auction site, has said it will not allow the resale of Olympic tickets.
Meanwhile, the Metropolitan Police's Operation Podium, which deals with Olympics-related fraud, says it is continuing to monitor the internet for ticket touts.