There is software around which is specifically designed to help certain individuals use engines when they play chess online. This is enough to put honest players off online competition, and I can understand why.
I don’t believe it will ultimately be stopped by cheating detection, I know of several people who have been accused of using engines in their online games when I am quite sure that they did not do so. Equally I’m quite sure that subtle use of engines is possible and that it will get below whatever radar is in use.
At the same time there is a positive side to playing people who cheat, we get stronger opponents. Obviously we don’t want to treat such games as ‘fair competition’, but for training purposes they are excellent. There’s not much point playing some dummy who makes elementary mistakes, it’s much better that they are engine guided. It’s true that the person employing the engine will get zero benefit from these games but then that’s not our problem. They get an ego massage by getting their ratings up (and it seems that some can overlook the fact that it wasn’t their own doing), we get better training games.
Of course we might not want our true identities to be known when losing to these cheats, which is why it’s best to play under a pseudonym. But if we do this the cheats can only help us improve.