This indicates an attack attempt to exploit a SQL Injection vulnerability in Symantec Web Gateway.
The vulnerability is due to insufficient sanitizing of user supplied inputs in the application when handling a malicious HTTP request with a crafted "id" parameter. A remote attacker can exploit this to send a crafted query to execute SQL commands on a vulnerable server.
Symantec Web Gateway 18.104.22.168 prior to database update 22.214.171.1248
Information Disclosure: Remote attackers can gain sensitive information from vulnerable systems.
Apply the most recent upgrade or patch from the vendor.