A 49-year-old man from Peacehaven has been arrested on suspicion of attempting to meet children under the age of 16 following grooming online.
He is on police bail until June 11 while enquiries continue.
Police had received six similar separate reports during December 2016.
Two other men have been arrested, a 40-year-old from Horsham and a 53-year-old from Horsham.
Two of the arrests took place in Burgess Hill, and the third took place in Crawley.
No children were actually involved in any of the cases.
Detective Inspector Rachel Carr said, “Each case is under active investigation, but we remind everyone of the dangers for them, and for others, of seeking to meet on line for sexual activity with under age children.
“You are vulnerable to arrest and to prosecution, as any attempts to abuse children are taken very seriously by investigators and by the courts.
“At the same time it is also important to say that we do not encourage members of the public to carry out investigations themselves, especially in such a sensitive type of case.
“They could jeopardise evidence, hinder chances of prosecution, or risk harm to themselves. Such matters should be reported to the police at the outset.
“Anyone else who has information about such activity is asked to contact us by emailing email@example.com Operation Abbotstone. You can also report online to https://sussex.police.uk/contact-us/response-to-appeal/ or call 101.
“Alternatively you can contact the independent charity Crimestoppers anonymously on 0800 555 111 (www.crimestoppers-uk.org).”