An internet service, called Craigslist, is losing the combat against the online scam rental ads according to a study.

The study was done by a set of researchers who, after examining two million ads in a five-month period in 2014, came to a conclusion that Craigslist were able to remove only less than half of the sources that likely weren't genuine.

The study is due to be presented at the Financial Cryptography and Data Security conference in Barbados next week.

Craigslist publishes instructions on its site, to help its users avoid scams. It cautions people to beware of ads that involve wiring funds over the Western Union, and advises to follow face-to-face transactions, which will help in keeping away from most of the trouble.

In order to differentiate the fake ads from the original ones, the researchers monitored the details including IP addresses, common bank account numbers and email addresses.

Credit report remains most common scam. They place a fake rental ad and, if a victim responds, directs them to pay for a credit report. If the victim pays, the scammers collect a commission.

In another scam, rental ads from other real estate websites were copied and advertised on Craigslist. But the rental cost was extremely lowered. The scammers asked for a bank transfer to cover a deposit and the first month's rent. The researchers found out that most of those scammers were in Nigeria, with some in the US

Taking everything into account, Craigslist missed the mark, to catch 47 percent of the rental ads that were scams, and for those that it did found out, it took a long time to flag them.

Of the listings cloned from other real estate websites, 60 percent stayed up for 10 hours, and 40 percent remained online for more than 20 hours, plenty of time to catch some victims. (pic courtesy: kycir.org)