Serious in-person competitions like ICPC are still effective against cheating. The first phase happens in a limited number of venues and the computers run a custom OS without internet access. There are many people watching so competitors don't user their phones, etc.

The Regional Finals and World Finals are in a single venue with a very controlled environment. Just like the IOI and other major competitions.

National High School Olympiads have been dealing with bigger issues because there are too many participants in the first few phases, and usually the schools themselves host the exams. There has been rampant cheating. In my country I believe the organization has resorted to manually reviewing all submissions, but I can only see this getting increasingly less effective.

This year the Canadian Computing Competition didn't officially release the final results, which for me is the best solution:

> Normally, official results from the CCC would be released shortly after the contest. For this year’s contest, however, we will not be releasing official results. The reason for this is the significant number of students who violated the CCC Rules. In particular, it is clear that many students submitted code that they did not write themselves, relying instead on forbidden external help. As such, the reliability of “ranking” students would neither be equitable, fair, or accurate.

Available here: [PDF] https://cemc.uwaterloo.ca/sites/default/files/documents/2025...

Online competitions are just hopeless. AtCoder and Codeforces have rules against AI but no way to enforce them. A minimally competent cheater is impossible to detect. Meta Hacker Cup has a long history and is backed by a large company, but had its leaderboard crowded by cheaters this year.