Blocking the entire
/8 would not only block a lot of legitimate GCE customers from accessing your site but would also block several other networks from accessing your site as the IP addresses in that range are owned by many different companies.
Even blocking individual IP addresses can cause harm as cloud products allow resources (including IP addresses) to be released when no longer in use and be reused for other customers.
Whois data provides information about who owns an IP range, what the exact range is, and what the procedure for handling abuse. In this case the procedure for handling abuse is to fill in this form: https://support.google.com/code/go/gce_abuse_report
The whois data as of this moment reads:
NetRange: 220.127.116.11 - 18.104.22.168
CIDR: 22.214.171.124/12, 126.96.36.199/13, 188.8.131.52/12
Parent: NET35 (NET-35-0-0-0-0)
NetType: Direct Allocation
Organization: Google LLC (GOOGL-2)
Comment: *** The IP addresses under this Org-ID are in use by Google Cloud customers ***
Comment: Direct all copyright and legal complaints to
Comment: Direct all spam and abuse complaints to
Comment: For fastest response, use the relevant forms above.
Comment: Complaints can also be sent to the GC Abuse desk
Comment: ([email protected])
Comment: but may have longer turnaround times.
In addition to filing an abuse report I suggest you audit your system for presence of any security flaws of the type attempted to be exploited as well as others that may be targeted next. Blocking IP addresses isn't going to keep you secure from attacks. A sufficiently persistent attacker will be able to attack you again from other IP addresses outside the range you have blocked.