![]() Disabling LLMNR closes a very serious risk vector. Problem is hackers realized the protocol didn’t have effective protections to prevent unauthorized nodes from authoritatively claiming they were anyone (everyone.) That said, in almost all cases LLMNR is no longer needed because proper DNS is configured. ![]() It made sense for quick resolution of names that were on the same subnet. It was useful back in the day when DNS servers required costly processing power and system admins didn’t want them in every subnet (still don’t!) AdHoc networks can benefit greatly from them as well, but AdHoc networks are pretty uncommon these days. What’s worse? The impersonator may forward that packet to the actual file-server, so the user never realizes anything is amiss. If that LLMNR received response was actually an impersonator (I’mEveryoneNotReally), Windows just disclosed that user’s credential hash to a third-party. If Windows attempts to use LLMNR to identify the server of a file-share and it receives a reply, it will send the current user’s credentials directly to that server assuming it wouldn’t have replied if it wasn’t the authoritative file-server. Windows (other operating systems too!) will use LLMNR in certain circumstances to identify certain machines on the network, such as file-servers. The client who is requesting the information will accept (and wholly trust) whoever answers first as the authoritative answer, because, based on the protocol specifications, the only responses it should receive are authoritative (and trustworthy.) ![]() Let’s call this evil node “I’mEveryoneNotReally.” This creates a race-condition for the client. What if you configure a node on the network to authoritatively say that it is, no matter what the query, exactly who the query is looking for. It does this by sending a network packet to port UDP 5355 to the multicast network address (all layer 2). It was (is) able to provide a hostname-to-IP based off a multicast packet sent across the network asking all listening Network-Interfaces to reply if they are authoritatively known as the hostname in the query. LLMNR was (is) a protocol used that allowed name resolution without the requirement of a DNS server. This one is a biggie, and you’ve probably heard Jordan, John, me, and all the others say it many many times. ![]() Link-Local Multicast Name Resolution (LLMNR) ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |