[CentOS] Server used in DOS attack on UDP port 0

Wed Nov 4 13:19:24 UTC 2015
Eero Volotinen <eero.volotinen at iki.fi>

Did you run basic checks like rkhunter and so on?

Is there password login enabled or only public key on ssh service.

Weak passwords on ssh is usually primary reason on system compromise.

4.11.2015 12.23 ip. "Andrew Holway" <andrew.holway at gmail.com> kirjoitti:

> 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
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