This indicates an attempt to access a sensitive file through HTTP requests.
The signature checks for these files:
/etc/passwd (List of local users)
/etc/shadow (List of users' passwords' hashes)
/etc/host (Host file)
These files in Linux system store essential information regarding registered users. Access to these files is usually restricted.
All HTTP servers that are not properly configured.
Information Disclosure: Remote attackers can gain sensitive information from vulnerable systems.
Monitor the traffic from that network for any suspicious activity.
Restrict access to the files.