Dan Dumitru Ciobanu was arrested while working in a photo developing lab after Romanian authorities traced the Blaster-F worm back to him with the help of researchers from Softwin SRL, a computer security company based in Bucharest.
Ciobanu could face a 15-year jail sentence if found guilty, under new Romanian laws designed to prosecute cyber criminals.
As with the arrest of Minnesota teenager Jeffrey Parson on Friday, Ciobanu's decision to use his online nickname, enbiei, for the virus file was integral to his capture, Softwin said.
Ciobanu's version of Blaster also included a caustic message, written in Romanian, in the body of the worm that named a local university, the Hydrotechnical University in Iasi, as well as one of his teachers.
As with the Blaster-B variant created by Parson, Blaster-F is a modest alteration of the original Blaster worm. Ciobanu's variant does not alter the worm's basic functionality and spreading mechanisms. Like the Blaster-B variant, that similarity made the F variant less successful at spreading, the company said.
Romanian authorities seized two computers from Ciobanu's home and are analysing their contents.
Romanian law enforcement officials and the FBI could not immediately be reached for comment on the arrest.
Paul Roberts writes for IDG News Service