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Network Security

Network Security. Network Security. Network security starts from authenticating any user.

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Network Security

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  1. Network Security

  2. Network Security • Network security starts from authenticating any user. • Once authenticated, firewall enforces access policies such as what services are allowed to be accessed by the network users. Though effective to prevent unauthorized access, this component fails to check potentially harmful contents such as computer worms being transmitted over the network. An intrusion prevention system (IPS) helps detect and prevent such malware. • IPS also monitors for suspicious network traffic for contents, volume and anomalies to protect the network from attacks such as denial of service.

  3. Firewall • A firewall is any device that is designed to restrict and control access to your computer and files. Both hardware and software can be used to restrict access to your computer or network. There are a number of software titles that will allow you to control access. Some of these firewalls are virtually invisible to you and run in the background, silently protecting your computer. Other firewalls protect you by alerting you to every potential security breach

  4. Brief History • Packets • Messages - such as e-mail messages or web pages - that are sent along the Internet are broken down into smaller packets of information. This is done because there is limited room for message transmission along the Internet. Keeping the messages to a standardized parcel size of fewer than 1500 characters ensures that traffic will continue to move smoothly. • Once the message is broken down into packets, each one is transmitted to the destination computer individually. Packets that make up the same message are often sent along different routes to its destination by the router depending on the amount of traffic on any given channel at the time of transmission. Upon arrival at the destination computer, the packets are recombined into the original message.

  5. Packet Headers Each packet is given a header that contains important information such as the address of the destination and of the source computer, the amount of data in the packet and how the packets must be recombined to form the original message. The header also contains information known as a checksum. The checksum is a numerical value based on the amount of information contained in the message.

  6. Pcket Filters - Evolution • First generation - packet filters: Packet filters act by inspecting the "packets" which represent the basic unit of data transfer between computers on the Internet. If a packet matches the packet filter's set of rules, the packet filter will drop (silently discard) the packet, or reject it (discard it, and send "error responses" to the source). • 2 Second generation - "stateful" filters or 'stateful firewall' maintains records of all connections passing through the firewall, and is able to determine whether a packet is the start of a new connection, or part of an existing connection. Though there's still a set of static rules in such a firewall, the state of a connection can in itself be one of the criteria which trigger specific rules. • 3 Third generation - application layer: also known as proxy based firewalls. The key benefit is that it can "understand" certain applications and protocols (such as File Transfer Protocol, DNS or web browsing), and can detect whether an unwanted protocol is being sneaked through on a non-standard port, or whether a protocol is being abused in a known harmful way. This type of filtering can be carried out by proxy servers, but if the filtering is done by a standalone firewall appliance, or in a device for traffic shaping, the technology is likely to be referred to as deep packet inspection.

  7. Others • Network address translation • Firewalls often have network address translation (NAT) functionality, and the hosts protected behind a firewall commonly have addresses in the "private address range" • NAT involves re-writing the source and/or destination addresses of IP packets as they pass through a Router or firewall. Most systems using NAT do so in order to enable multiple hosts on a private network to access the Internet using a single public IP address • Access Control Lists (ACL) • In computer security, an access control list (ACL) is a list of permissions attached to an object. The list specifies who or what is allowed to access the object and what operations are allowed to be performed on the object. In a typical ACL, each entry in the list specifies a subject and an operation: for example, the entry (Alice, delete) on the ACL for file XYZ gives Alice permission to delete file XYZ. • In an ACL-based security model, when a subject requests to perform an operation on an object, the system first checks the list for an applicable entry in order to decide whether or not to proceed with the operation.

  8. Security threats software Spyware • When you install any software that is free, you should suspect that it might be spyware. This means that the software can gather information about your computer and how you use it and send that information to marketing companies. Those companies can gather information such as your email address, calendar data, web sites you have visited, or what music you listen to. Spyware removal • If you notice that your machine is running slower than normal or the command prompt box appears on your screen you may have spyware on your computer. To deactivate the spyware, you may want to install anti-spyware software such as "Ad-Aware" or "Spybot".

  9. Viruses You can prevent most viruses by following these five commandments: • 1. install anti-virus software. • 2. avoid using floppy disks to transfer files from one computer to another. • 3. Do not open files from any email before checking the file with an anti-virus program. If you need to receive files via email, be careful to check the file extensions. This is not a foolproof protection, but you should know that if you receive a file with the .exe extension, you should never open it. • These are usually programs that can either be spyware, viruses, or trojans. Trojans are malicious software programs (also called "malware") that might do things such as erase files from your hard drive. • 4. Be sure you know the source of your software. If you aren't sure the software distributor is legitimate, don't take a chance and install the free software, no matter how amazing it seems. • 5. Do not download free music, movies, or media files. These types of files (along with other types of free images, media files or movies) often have a catch. The catch is that there can be viruses embedded in these files. If you download free music or media, be aware that at the very least, the sites will drop spyware on your machine. • Following these commandments will help you prevent virus infection

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