I just visited a forum and a member knew what OS I was running without me saying anything (a not TOO common distro of linux). Now I'm not sure how he exactly he might have done it, or what information he might have been able to get out, but, for starters, I'm guessing that, besides information on my OS, they might have been able to determine other things such as my ip address, general location, browser, and even browser cookies. Whether or not it was necessary, I deleted my browser, performed a scan with both chkrootkit and rkhunter, and will never get back on that site. Heck, I'm wondering if by posting here so soon after, I'm putting myself at risk.
I guess the questions burning in my mind are: can they pose a threat to others in my network assuming there is a firewall and wpa2 security type? I don't have any real important information in my system, and I don't really do anything that might really put me at real risk besides the odd online purchase, but I don't know what others might have in their systems.
Should I be able to keep doing those normally until I see something weird? Besides what I already mentioned, what other steps should someone in this situation take?