If an attacker manages to access a firewall or a corresponding administration interface, they may manipulate data in any number of ways. For example, they may change the configuration, start additional services, or install malware. They may also eavesdrop on communication links in the manipulated IT system. The firewall's rules may also be changed in a way that makes it possible to access the firewall and the respective organisation’s intranet from the Internet. Furthermore, an attacker may start a denial-of-service attack (DoS) by using the firewall's rule set to prevent access to individual server services.