"This assignment is a sign of the importance we attach to Eurojust, Europol and EC3, and we look forward to assessing together whether this should be a permanent arrangement in the future," Attorney General Loretta Lynch told EC3 officials Wednesday at The Hague.

The placement is just one part of the increasing partnership between U.S. and European law enforcement.

In July, the two teams worked together with to bring down an elite, underground hacking forum known as Darkode, arresting dozens of members around the globe.

And last November, the two teamed up to lead a major bust of dark market websites operating on the largely anonymous Tor network selling narcotics, firearms, stolen credit card data, fake passports and hacking tools.

Lynch said these victories for law enforcement are possible, in part, by increasing cooperation.

The FBI, she noted, has placed three new permanent Cyber Assistant Legal Attachés in foreign offices, including London, Ottawa and Canberra, Australia.

"Those attachés are embedded in law enforcement and intelligence agencies in their host nations to help facilitate information-sharing, improve cooperation on investigations and build even stronger relationships with our allies," Lynch said.