Fraud can still occur when someone signs on using another person's password. Make sure your system has an automatic lockout feature. After failing to enter the correct password three times, the person has to call the boss to gain access. Require passwords to be comprised of both letters and numbers, no names or words from the dictionary. Also, require employees change passwords periodically.
Most systems have audit functions that track who is responsible for specific data.
Companies do not turn these trails on because they can slow the system. Prioritize what needs to be audited the most. Then turn on the audit function only for those specific data fields. Have staff read and sign a policy covering the do's and don'ts of system usage, including everything from Internet use to passwords. These policies are getting more affordable as insurers target sales to small businesses.