Network File System (NFS) - remote filesystem access [RFC 1813] [RFC5665]. A commonly scanned and exploited attack vector. Normally, port scanning is needed to find which port this service runs on, but since most installations run NFS on this port, hackers/crackers can bypass fingerprinting and try this port directly.
shilp also uses port 2049 (UDP).
FreeBSD is vulnerable to a denial of service attack. A remote attacker could send a specially-crafted NFS Mount request to TCP port 2049 to cause a kernel panic, resulting in a denial of service. References: [CVE-2006-0900] [BID-16838]
Stack-based buffer overflow in nfsd.exe in XLink Omni-NFS Server 5.2 allows remote attackers to execute arbitrary code via a crafted TCP packet to port 2049 (nfsd), as demonstrated by vd_xlink.pm. References: [CVE-2006-5780] [BID-20941] [SECUNIA-22751]
Novell Netware is vulnerable to a stack-based buffer overflow, caused by improper bounds checking by the xnfs.nlm component when processing NFS requests. By sending a specially-crafted NFS RPC request to UDP port 2049, a remote attacker could overflow a buffer and execute arbitrary code on the system or cause the server to crash. References: [XFDB-72199]
Notes: Port numbers in computer networking represent communication endpoints. Ports are unsigned 16-bit integers (0-65535) that identify a specific process, or network service. IANA is responsible for internet protocol resources, including the registration of commonly used port numbers for well-known internet services. Well Known Ports: 0 through 1023. Registered Ports: 1024 through 49151. Dynamic/Private : 49152 through 65535.
TCP ports use the Transmission Control Protocol, the most commonly used protocol on the Internet and any TCP/IP network. TCP enables two hosts to establish a connection and exchange streams of data. TCP guarantees delivery of data and that packets will be delivered in the same order in which they were sent. Guaranteed communication/delivery is the key difference between TCP and UDP.
UDP ports use the Datagram Protocol. Like TCP, UDP is used in combination with IP (the Internet Protocol) and facilitates the transmission of datagrams from one computer to applications on another computer, but unlike TCP, UDP is connectionless and does not guarantee reliable communication; it's up to the application that received the message to process any errors and verify correct delivery. UDP is often used with time-sensitive applications, such as audio/video streaming and realtime gaming, where dropping some packets is preferable to waiting for delayed data.
When troubleshooting unknown open ports, it is useful to find exactly what services/processes are listening to them. This can be accomplished in both Windows command prompt and Linux variants using the "netstat -aon" command. We also recommend runnig multiple anti-virus/anti-malware scans to rule out the possibility of active malicious software. For more detailed and personalized help please use our forums.
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-TCP port 2049: The default port of NFS server listening. UDP port 2049: The default port of NFS server listening. -TCP/UDP port 111: RPC binding port is used to establish connections between clients and servers.
The NFS version 3 protocol that uses UDP is given higher precedence than the NFS version 2 protocol that is using TCP. You can manually select both the NFS protocol version and the transport protocol with the mount command.
netstat -a : This will display all connections and listening ports. netstat -t : Displays only TCP connections. netstat -u : Used to display only UDP connections.
What decides? The intended use and the requirements for the transport. If you need guaranteed delivery and latency is not an issue, you choose TCP. If you can tolerate packet loss or prefer no state on the server, you might use UDP (which means you might need to handle packet reordering).
UDP is faster than TCP but is also more error-prone. The reason is that UDP doesn't use such an acute checking of packets as TCP and employs a more continuous data flow. TCP sends its data in sequence, so it uses more flow control.
NFS v4 generally only requires 1 port to be open, TCP destination port 2049 at the NFS Server side. This allows clients to initiate connections to it. In some rarer cases, NFS 4.0 servers might need to contact an NFS client on a separate connection, in the opposite direction, initiated from the NFS Server's port 2049.
According to RFC 6056, the ephemeral port range should be 1024-65535. However, if we only allow port 1024-65535 for outbound traffic on the NACL of the subnets where EFS locates, we will get timeout when we try to mount the EFS from an EC2 instances from a different subnet (same AZ).
Open the /etc/default/nfs-common file for editing: See more code actions. Dismiss View. Light code theme. Dark code theme. sudo nano /etc/default/nfs-common.
Set the STATDOPTS option: See more code actions. Dismiss View. Light code theme. Dark code theme. STATDOPTS="-p 2046"
Basically MGCP utilizes three Layer 4 protocols. Two of them UDP, and the other TCP. The UDP port 2427 is used for Call Control setup and teardown, and the other 2727 is used for the Calling Agent. TCP port 2428 for back hauling and keepalive traffic to the Call Manager cluster.
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