The online auction site pinpoints these three countries as the source of the majority of phishing e-mails that target eBay users for personal and account details.
Mark Lee, trust and safety manager for eBay UK, blamed the fact there was "no fear of real punishment" in the countries and highlighted the particular scale of the problem in Romania.
"These attacks are definitely organized," Lee said. "There are towns in Romania where the entire focus is on sites like eBay as the main source of income."
In June, eBay revealed details of athat led to several hundred arrests.
Most of Romania's law-enforcement efforts are concentrated on its capital, Bucharest. But most of the cases that eBay identified during the crackdown originated from smaller towns, where the eBay team sometimes found backlogs of 200 eBay-related fraud cases, Lee said.
Speaking at the e-Crime Congress 2008 last week in London, Lee said .
But, Lee added, eBay has kept the number of attacks static through educating users about revealing personal details and built-in security measures in new Internet browsers.
Lee said that eBay is often successful in tracking down the smaller online criminals but he warned that fighting larger crime networks remains an "uphill battle."
Nick Heath of Silicon.com reported from London.