I recently installed an extension for Chrome called Hola (skip to next paragraph if you know it). It calls itself a VPN, but is basically a proxy pool AFAIK. You can choose a country from a list in a per website basis and your connection to that website comes from an IP from the selected country from there onwards. Meanwhile, you serve as a proxy for other users.
I tried using it at my uni but it was stuck at "initializing", and after a few tests (different browsers, different computers) I could only conclude that it was being blocked somehow. Which made me wonder: My computer is in a vulnerable position if it can be used by others as a proxy, possibly without my knowledge. So I was wondering which aspect of my network I need to configure in order to avoid this kind of thing. I am currently using this script to generate my firewall rules (iptables):
# Flush all rules iptables -F iptables -X # Allow unlimited traffic on localhost (breaks MPI programs otherwise) iptables -A INPUT -i lo -j ACCEPT iptables -A OUTPUT -o lo -j ACCEPT iptables -A FORWARD -o lo -j ACCEPT # Allow SSH traffic iptables -A INPUT -p tcp --dport 22 -m state --state NEW,ESTABLISHED -j ACCEPT # Allow incomming traffic from estabilished and related connections iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT # Policy: Allow outgoing, deny incoming and forwarding iptables -P OUTPUT ACCEPT iptables -P INPUT DROP iptables -P FORWARD DROP
I imagined the drop policy in "forward" would be enough, but it doesn't seem so. Is there anything I can do at the firewall level to block things like Hola? If not, what should I be doing?