Someone actually managed to hack into my Linux box yesterday through some SSH hole. Luckily I didn't have my wallet sitting around. I'm amazed that the hole was there by default (I installed SSH and figured it would only work for my username).
The only one of my Linux machines that got hacked was hacked in a similar way, except it was a VPS and my mistake was not realising that HyperVM was sneakily resetting my root password to the provider-set default of "changeme" behind my back. (Surprisingly, even then it seems it took several days for anyone to actually brute-force their way in.)