Instagram provides a feature to review your account's login activity, which is a useful tool to spot unauthorized access. Go to 'Settings' via your profile, select 'Security', and then 'Login Activity'. Here, you'll see a list of locations and devices that have accessed your account, along with dates and times. If you notice any unfamiliar activity, it's a strong indication that your account security may be compromised. Immediately change your password and review your account's security settings.