QTC allow me to point out that the network is actually named Tor and that it is no longer an acronym for the onion router. Tor is actually not technically an onion router either, although it is very frequently called one. These points are mostly unimportant trivia. Bridges are imo very important for vendors to be using. When you load Tor your client directly bootstraps at one of about eight directory authority servers. These servers are run by people that the Tor devs trust (and they need to trust them because if four of them are pwnt by the same attacker at any given time, and the attacker also has access to a (fairly) large amount of bandwidth, they can deanonymize large percentages of the Tor network as well as intercept large percentages of exit traffic. It is worth noting that they could not do this without being detected in a fairly short period of time). It is probably not that hard for an attacker to monitor some of the directory authority servers, the federal police of a country can almost certainly monitor all connections to and from any directory authority server in their country. I think several are in USA and Germany. Monitoring connections to and from directory authority servers allows an attacker to enumerate Tor client IP addresses, an attacker who can Monitor all directory authority servers can enumerate the IP address of every single non-bridged Tor client. When you use bridges they act as directory guards as well as entry guards. Unlike Tor directory authority nodes and normal entry guards, there is not an easily available list of all bridge node IP addresses (although some of the Tor devs have access to this information, as well as hackers who can pwn bridge distribution servers or mechanisms) and most attackers can only enumerate some percentage of bridge nodes (I think China blocked something like 85% of them last time I checked). Also, there are several hundred bridge nodes (maybe even over a thousand now) so it is much harder to monitor all of them than 8 directory authority servers, even if you could enumerate all of their IP addresses. Why do you not want your IP address to be identified as connecting to the Tor network? This is mainly a problem for vendors and for those who use fake ID boxes to maintain anonymity. There are really not that many Tor users in the grand scheme of things, versus the total world population. Also Tor users are fairly widely dispersed through out the world. In any given fifty mile radius there are not likely to be many Tor users. Since vendors must leak rough geolocation intelligence when they ship, an attacker who can place an order from a vendor (and make a one hundred mile radius around where it was shipped from) and can also enumerate Tor client IP addresses, can then intersect these two datasets together to narrow in on 'people who are likely the vendor'. The two datasets are A. Lives within a one hundred mile radius of where the package was shipped from and B. Is a user of the Tor network. The resulting crowd from this attack is not likely to be substantially large, particularly in more rural areas with less population density. It may even be the dreaded crowd size of one. This sort of attack is generally called an observability or membership revealment attack (as it relates to enumerating Tor client IP addresses). The other part is called an intersection attack (taking two or more datasets and removing items that do not appear in both to make a third dataset, as a technique for narrowing in on a target that is associated with a few data points of a known or estimated uniqueness). Bridges also increase security from a number of other attacks. They also reduce anonymity from a number of other attacks. One thing to worry about is an attacker who can identify bridged connections. If you use bridges in a country that doesn't restrict access to the Tor network, particularly from a residential location, the chances of you trying to protect from the previously mentioned sort of attack are high. In this case using a bridge would be worse than not using a bridge, since in addition to being identified as a Tor user you are identified as a Tor user who is worried about this sort of attack. Anyway, if you are worried about the very serious attack I mentioned I suggest that you use bridges. Also, bridge use probably slightly reduces your protection from a few sorts of attack, however it also increases protection from a few sorts of attack, and it also adds *any protection at all* against numerous other attacks.