Abstract: This study highlighted the importance of security measures and therefore, takes a look at a practical solution to security lapses on networked systems. Existing computer systems that had only users authentication were examined and resolved to design software that can serve as a security measure to computers that are linked to one another and those connected to the Internet. The software (Program in Visual Basic 6.0) called a Firewall was developed. On implementation it was found that if a known Trojan is detected during communication, it kills and terminates the process, but if none found, it allow communication by confirming the information source.