By providing the public with online computing facilities, librarians make available a world of information resources beyond their traditional print materials. Internet-connected computers in libraries greatly enhance the opportunity for patrons to enjoy the benefits of the digital age. Unfortunately, as hackers become more sophisticated and software gets more complex, online security threats escalate as well. Keeping shared public access computers (PACs) safe has become more challenging than ever. There is no practical way to guarantee that a computer in a public setting can be immune to threats and no user on such a computer can surf the Internet risk-free. If a proactive approach is taken to protect the health of the computing system and the users, the security risk can be mitigated before painful damage occurs. Waging the battle against hackers' threats can be difficult and expensive in terms of hardware and software costs and personnel resources. An ounce of prevention--a few relatively simple steps carried out on a regular basis--can make a big difference. In this article, the author outlines some common considerations to tighten up security for a PAC. Of course, each library has its own unique situation, and procedures can vary.