Hi,
One of our AWS machines was used in an DOS attack last night and I am looking for possible attack vectors. AWS tells me it was sending UDP port 0 traffic to a cloudflare address.
This instance had an incorrectly configured AWS security group exposing all ports.
The server in question is a Centos 7 based FreeIPA server, OpenVPN concentrator and DNS server.
With a brief inspection before the instance was stopped no evidence of intrusion could be detected in the obvious places and the machine is protected by standard SELinux policies.
On this machine Firewalld is currently configured with a single zone with masquerade enabled
firewalld config. public (default, active) interfaces: eth0 sources: services: dhcpv6-client dns http https kerberos kpasswd ldap ldaps ntp openvpn ssh ports: 81/tcp masquerade: yes forward-ports: icmp-blocks: rich rules:
Thanks,
Andrew