IDS and IPS have signature database. A signature is a set of rules designed to detect known attacks. The structure that presents this set of rules centrally is called the signature database. An open source signature database link is shared below. These databases are constantly updated against newly formed attack vectors. Network activities that trigger these signatures can be blocked or only detected according to the determined action of the signature. In other words, IDS and IPS are the same device/product, but 2 different concepts/terms emerge according to the action in the signatures. Many firewall manufacturers can provide the IDS / IPS module with an additional license in their products. Snort or Suricata are two well known open source IDS/IPS solutions in the market.
You can access the source of open source code signatures from the link below: