The press release (via Google Translate) issued by the agency in the wake of the arrest mentioned only the initials of the arrested man - L.M.L. - but stated that he was suspected of having repeatedly and without authorization accessed email accounts belonging to public figures in Romania, accessed confidential emails and transferred them to his computer, then changed the accounts' passwords.
He also stands accused of disclosing some of this collected information to the public in order to damage the reputation of the targeted persons.
A hint that the man in question might be "Guccifer" lies in the statement that US authorities helped in the investigation.
As you might remember, Guccifer has targeted online accounts of, among others, the chief of the US National Nuclear Security Administration, the Bush family, and Sex and the City author Candace Bushnell.
The press release also states that the arrested man was previously arrested for similar offences.
Romanian news outlet Gandul.info (via Google Translate) has dug up more information about the arrested man, naming him as one Marcel Lazarus Lehel. Judging by the description of his modus operandi in his 2011 attacks, the police seems to have gotten the right man.