A man from Birmingham was questioned by police over claims he harassed a woman through Facebook.
The victim made a complaint of online harassment to Sussex Police, claiming she received abuse while using her Facebook account, which she said had also been hacked.
The woman also said her emails had been hacked into by an unknown source, police said.
A spokesman said officers examined the woman's computer as part of an ongoing investigation to trace the source of the abuse and security breach.
The 32-year-old man from Bournville, Birmingham. He has been bailed until October 19 pending further inquiries.