So you have found plagiarized papers and don’t know who to contact to report your findings? Here are pointers for some of the relevant publishers of Computer Science literature:

• IEEE: FAQ and email address
• ACM: Plagiarism policy and email address
• Springer: Contact form
• Elsevier: I could only find out that authors should contact the editors of the publication.

If you have anything to add, feel free to add a comment or drop me a message. Thank you!