Not the answer you're looking for, but. Any version of macOS not currently receiving security updates (i.e., anything pre-El Capitan) has unpatched remote root exploits, and as such must be air-gapped from any network with Internet connectivity - not just for your sake, but for the health of the Internet as a whole.
At that point, Mac users using OS X 10.6 Snow Leopard, 10.7 Lion, and 10.8 Mountain Lion will be left behind by the current versions of Firefox. It will be a sad day, as Firefox is the last major browser to support Mac OS X 10.6 through 10.8.
If you need Internet connectivity, you either need to install an actively-maintained Linux distro, or upgrade to a Mac that will run macOS Sierra. (El Cap will lose security support when macOS High Sierra ships this fall.). In this context means that it never gets connected to any network with Internet connectivity; the only devices it ever interfaces with are devices that you control and trust.
That way, you do need local access to the computer in order to get access to it, and it can't be used as a 'bot' or what-have-you to launch attacks on other Internet users. Today isn't like the old days before Internet access was ubiquitous, when older computers and older software could still be used for everything they did when they were new. Now, anything that isn't actively being patched is a security risk to its user and a health risk to the online community as a whole. Air gap (networking) An air gap, air wall or air gapping is a network security measure employed on one or more computers to ensure that a secure computer network is physically isolated from unsecured networks, such as the public Internet or an unsecured local area network.
The name arises from the technique of creating a network that is physically separated (with a conceptual air gap) from all other networks. The air gap may not be completely literal, as networks employing the use of dedicated cryptographic devices that can tunnel packets over untrusted networks while avoiding packet rate or size variation can be considered air gapped, as there is no ability for computers on opposite sides of the gap to communicate. Downvote to remove v0.24.