Category Archives: Firewalls

Setup an OpenVPN server with certificate and two-factor authentication on CentOS 7

Introduction My goal was to have an OpenVPN server running, to which i can connect using different ports and by pipping it over an IP over ICMP tunnel (the latter will follow in another post). Ports i want to use: 1194/udp – The default OpenVPN port 53/udp – If im lucky and the network has DNS open by default… 1195/udp … Continue reading

Posted in CentOS, Firewalls, Linux, OpenVPN, Security, VPN | Tagged , , | 1 Comment

Limit/prevent SSH brute force attempts

If you (have to) run a public available SSH server, you may have noticed already that there are a lot of brute force attacks trying to guess a user and password (have a look into /var/log/secure ). If you did it the correct way, you only allow public keys to authenticate of course. But maybe you can’t, because the client … Continue reading

Posted in CentOS, Firewalls, Linux, Security | Tagged , , , , | 1 Comment

Quick tip: Limiting RPC dynamic port range

One annoying thing with RPC is, that it is configured to use over 16’000 ports by default (in 2008 Server). That’s absolutely not needed in most cases. I normally limit the range to 1000 ports which is more than enough, and makes firewall administrators a bit more happy… a bit… To change the port range to f.ex. 43000-43999 you have … Continue reading

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