Network file system (NFS) is a computer protocol that describes how to connect and access files via a network connection. It is used to store and share data, but early versions of the protocol do not provide or request user-based authentication.
Since the fourth version, NFS has been using Kerberos to improve authentication. Unfortunately, this version has not been widely implemented, leaving some holes that are catching the attention of experts — and cybercriminals.
NFS Servers Leak Data Like a Sieve
Security research firm Fortinet recently took a look at NFS, and its conclusions are rather worrisome. It found that “most servers on the Internet that have been linked to data leakage have been shown to use NFSv3.”
Fortinet used data from the website Shodan and found that 10 percent of NFS servers in the world are open for everyone to access with no need for a password. Some of these servers contained confidential data such as email backups, server logs and web source code.
This isn’t limited to just read-only access, either; Fortinet found that write access is often available as well.
Thousands of the exposed servers were located in the U.S. (18,843 servers), China (11,608), France (10,744), Germany (7,188) and Russia (5,269), the firm reported.
Mitigating the Risk
Fixing this problem can be a bit tricky. Fortinet strongly recommended upgrading NFS to version 4, but this isn’t possible for every organization.
If one of the earlier versions of NFS must be used, then there should be a specific white list of allowed IP addresses that can access the data. While the security firm noted that “this process can be tedious and time consuming,” it is a critical part of establishing “data security protocols that will prevent sensitive or confidential data from being accessible from the internet.”
Enabling the NFS application control signature on a system’s main gateway can also block all unexpected NFS connections from the outside to prevent data leakage.
Correct NFS configuration can be a pain for the system administrator, but saving a server from exploitation by cybercriminals will be worth it.