Firewalls are a threat prevention tool that block malicious content from entering your network. Like antiviruses and other security tools, they are just one layer of defense in your entire IT infrastructure. Technology like SIEM, on the other hand, provides overall monitoring and analysis. SIEMs often uses the information of firewalls and other tools to construct a full picture of security and assist IT professionals in mitigating threats as soon as they are identified. SIEMs are not meant to replace your firewalls and antiviruses but work in conjunction with them to provide you with greater security.