In: Categories » Computers and technology » VPN » Attacks over TCP and UDP ports
A port number is a virtual “mail slot” on each of these machines. Applications running on computers listen to the Internet for incoming information on these ports. Certain applications listen on certain ports.The Internet Assigned Numbers Authority (IANA [www.iana.org]) defines these ports (e.g.,Web servers listen on ports 80 and 443 and File Transfer Protocol (FTP) servers listen on port 21. Hypertext Transfer Protocol (HTTP), Hyper-Text Transfer Protocol Secure sockets (HTTPS), and FTP are examples of Internet Protocols.You will never find a legitimate FTP server listening on port 80. Ports 1 to 1023 are considered well-known ports, and have clearly defined IP’s. Ports 1024 through 49151 are registered ports. Specific software vendors have registered these ports for use by their specific applications. Ports 49152 to 65535 are dynamic ports.These have no specific registration and can be used by any application at any time. Using either or both application and gateway firewalls mitigates the misuse of ports.
Ports can use either the TCP protocol or the User Datagram Packet (UDP) protocol. TCP requires a connection started with a SYN packet that receives an ACK packet in response. SYN-ACK continues until the end of the data transmission. Each ACK packet confirms the correct receipt of the SYN packet containing data. On the other hand, UDP protocols send data with no requirement for a response. UDP protocols are generally faster than TCP protocols, but there is no assurance that the data has arrived at its destination intact. RFC 1700 documents, the official well-known port assignments, are available on the Web. The IANA makes the port assignments. In general, a service uses the same port number with UDP as with TCP, although there are some exceptions.The assigned ports were originally numbered from 0 to 255, but were later expanded to 0 to 1023.
legal notice
Our website is not responsible for the information contained by this article. Web-articles is a free articles resource.
Suggestion: If you need fresh, daily updated content for your website, feel free to use our service. Click here for more information.
Useful tools and features
If you like this article (tutorial), please link to it from your web page using the information above.
related articles
Who Needs Remote Access? Determining who needs to use your VPNs is not an easy task that can be done in just minutes. It is not uncommon for almost every employee to need some form of VPN access at one point or another.This introduces many challenges from user management to the auditing of your systems and individual access logs.This is an area in which your user groups and centralized user management systems will play an important role. It will help ensure your access rights are secure and grant...
2. Attacks can be divided into three main categories
Attacks Attacks can be divided into three main categories: - Reconnaissance Attacks Hackers attempt to discover systems and gather information. In most cases, these attacks are used to gather information to set up an access or a Denial of Service (DoS) attack. A typical reconnaissance attack might consist of a hacker pinging Internet Protocol (IP) addresses to discover what is alive on a network.The hacker might then perform a port scan on the system to see which applica...
3. System and Software Exploits
System and software exploits allow hackers to take advantage of weaknesses of particular OSs and applications (often called bugs). Like protocol exploits, they are used by intruders to gain unauthorized access to computers or networks, or to crash or clog up the systems to deny service to others. Common bugs can be categorized as follows: - Buffer Overflows Many common security holes are based on buffer overflow problems. Buffer overflows occur when the number ...
4. Types of attack and protocols
Phishing, the new information gathering technique, is spreading and becoming more sophisticated. Phishing e-mails either ask the victim to fill out a form or direct them to a Web page designed to look like a legitimate banking site.The victim is asked for personal information such as credit card numbers, social security number, or other data that can then be used for identity theft.There has been at least one insidious phishing scheme that uses a Secure Sockets Layer (SSL) certificate so that the data...
Firewall Types There are two basic types of firewalls: Application Proxy and Gateway. Gateways are divided into packet filters and stateful inspection firewalls.These differ in function and design and have different uses in network architecture. Never try to have one type of firewall do the duty of another type. It is better to have a well-run and securely configured firewall doing its intended job, than to have something doing a job for which it wasn’t designed.This is an invitati...
6. The inspection of TCP IP packets
The Inspection Process The inspection of TCP/IP packets is a multi-step procedure. What follows is a summary of the steps, not necessarily in order : 1. A packet arrives at the outside interface. It is checked for permitted or denied ports and IP addresses. Note that stateful inspection firewalls require both a port and an IP address. IP addresses can be in the form of a single machine, group of IP addresses, or “any,” meaning any valid IP address on the spec...
7. Lower Data Transfer Rates Than a Packet Filter
Networking Standard A stateful inspection firewall is the de facto standard for network protection at this time. Installing less is not a wise move without good reason (e.g., a requirement for the fastest possible data transfer while maintaining some protection for the internal network). Performance and Protection The balance of performance versus protection between a packet filter and an application proxy is excellent. Since stateful inspection is the curre...
8. RFC 959 specifies the commands that a minimum implementation
Minimum Implementation RFC 959 specifies the commands that a minimum implementation of FTP must support, and RFC 1123 updates this list with additional commands. The implementation specified by RFC 1123 is more capable in handling communications between computers that may use different operating systems, file systems, and firewall protection. However, RFC 1123 says that computers whose operating system or file system doesn’t allow or support a command aren’t obligated to add support for it. So f...
9. Four Rules for Securing Your Devices and Local Network
Paying attention to the following four rules will go a long way in ensuring that your device, data, and local network are as secure as possible from security risks: 1. Use a firewall and configure it with the most restrictive settings that allow your device to perform the communications it requires. 2. Restrict access to individual protected resources with user names and passwords. 3. Validate data provided by users to ensure the contents won’t cause harm. 4. Encrypt data that must rema...
10. VPN service suppliers may offer best effort performance
Virtual private network (VPN) A virtual private network (VPN) is a computer system in which several links between nodes are passed by open connections or virtual circuits in various bigger networks (for instance the Internet), as different to running transversely a single private network. The Link Layer protocols of the virtual network are believed to be tunneled through the transfer network. VPN service suppliers may offer best-effort performance, or may have a definite service level agreement (SLA) with their VPN clients....