الخميس، 27 ديسمبر 2012
IT Infrastructure Security Issue -Step by Step
It is said “Defense is in Depth”.This security model is represented in the figure below. This model consists of 4 layers of security
This layer is like the four walls and the roof of a secure house. It includes firewalls, routers and proxy servers. A national survey showed that 70-80% of attacks are internal i.e., from within the organization’s internal network. Therefore, securing from internal attacks is the first line of defense. However, having only this line is not enough to protect any network and valuable information.One of the common attacks on this layer is DoS (Denial of Service) attack, which involves flooding the point of connection to outside world with unproductive traffic. common DoS attacks on routers are Smurf, Syn, Ack and Rst attacks. Cisco researchers/security analysts have produced a wonderful document (Refer: http://www.cisco.com/warp/public/707/21.html) on how to configure a router to protect against these attacks. There are numerous solutions documented by various vendors. I have discussed the Cisco’s findings here since I am implementing and managing the same in my organization.The aforesaid paper describes how attacks like Smurf target victim systems using source-spoofed packets originating from a third-party’s (middle) system. One of the methods to stop this involves filtering at the point of connection to the Internet in your network or your ISP. Additionally router vendors have added options to disallow packets with spoofed IP source addresses. Cisco has implemented this by adding a command: “[no] ip verify unicast reverse-path”.To prevent one’s system from being the middle system (the system used to attack the target), Cisco has added another command: “no ip directed-broadcast” in IOS 12.0. This option is set by default, and protects the OSI layer3 broadcast into OSI layer 2 broadcast.If you have a DMZ, make sure the filters between your internal network and DMZ are configured properly:- DMZ is setup as an external network to the internal network (production network)
There are different flavors of UNIX. Linux is one of the widely used and popular variant of UNIX. Like any other operating system, we have to keep fine-tuning Linux too. Some of the precautionary measures related to Linux systems security are as follows:
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الثلاثاء، 25 ديسمبر 2012
IT Infrastructure Security
IT Infrastructure Security
IT security is a multi-discipline subject requiring a number of different skills sets and knowledge areas. A key area of knowledge which is vital for any security specialist is a clear understanding of IT infrastructure and how it relates to the creation of a comprehensive security strategy.
Understanding Firewalls
Much like a firewall in real life protects parts of a building from a spreading fire, an IT firewall protects computer systems from the dangers posed by an internet connection. A firewall is essentially a component located between a computer or a network of computers and the internet. The specific purpose of a firewall is to prevent unauthorized access to the computer systems it is configured to protect. Firewalls take the form of software, hardware or a combination of both and are not limited to use by large companies. Anyone who owns a computer (including home users) that is connected to the internet for even short periods of time should have a firewall configured.
A good security strategy should consist of multiple layers of protection and in such a scenario the firewall is typically the first line of defense.
Firewalls fall into three main categories - Packet-filtering, Proxy-service and Stateful-inspection firewalls, each of which will be covered in detail here.
Proxy Service Firewalls
A proxy service firewall is placed between the internet and an internal network of computers and acts as a go-between for the two environments. With a proxy service in place, internal client computers do not connect directly to outside resources. Instead they connect to the proxy server which in turn connects with the external resource on behalf of the client, thereby masking the internal IP address of the client. Any responses from the external resources are handled by the proxy service which passes them along to the client that originally requested the data.
Under such a scenario no internal systems are ever in direct contact with a remote server or service and all internal IP addresses are masked by the proxy server. Proxy servers can also provide caching functions, where web pages that are frequently accessed by internal clients are stored by the server such that they can quickly be supplied when subsequently requested leading to faster response times. Proxy service firewalls are available in two basic forms, Circuit-level gateway which works at the Session layer of the OSI model to verify that all sessions are legitimate and Application level-gateway which works at the OSI Application layer to control traffic of particular types (such as HTTP, FTP and SNMP).
Stateful Inspection Firewalls
Stateful-inspection firewalls (also known as dynamic packet filtering firewalls) operate at the OSI Network layer and combine some features of both packet-filtering and proxy server firewalls. A stateful-inspection firewalls not only examines the header information of packets, but also monitors sessions to ensure that they are legitimate and maintains state tables for each connection. Using these state tables, every packet received by the firewall can be viewed within the context of preceding traffic, allowing malicious data to be intercepted and blocked.
Routers
Routers are devices used to connect different network segments and operate at the OSI Network layer. Routers operate by examining each received packet and using algorithms together with routing tables to determine the optimal path for the data to reach its ultimate destination. Routers essentially form the backbone of the internet. Routing tables are either updated manually by an administrator, for configured automatically using a variety of different protocols including Routing Information Protocol (RIP), Interior Gateway Routing Protocol(IGRP), Enhanced Interior Gateway Routing Protocol (EIGRP) and Open Shortest Path First (OSPF).
Routers also include some security in the form of Access Control Lists (ACLs) which drop packets based on pre-defined rules, stateful-inspection and packet filtering.
Perhaps the biggest potential security risk for routers involves remote access to internal functions and configuration options. Due to their distributed nature all routers provide remote administration features. It is essential, therefore, that strict password conventions are implemented and that encrypted communications are used when logging into a remote router.
Switches
Most switches operate at the Data Link layer (layer 2) of the OSI model (although newer models are now moving up to the Network Layer) and are the basis of most Ethernet based local networks. Each port on a switch is a separate collision domain making switches much more efficient than Hubs where all ports are on the same collision domain (whereby data for a specific network client is broadcast on all hub ports, not just the port to which the destination client is connected). Routing is based on the MAC addresses of devices connected to the switch.
As with routers, administrative access to switch devices must be carefully controlled using strict passwords and secure communications protocols during remote access.
Wireless
Starting with wide spread deployment in home networks, Wireless Access Points and corresponding wireless network adapters have now begum to appear within business enterprises. This progress has accelerated considerably since the introduction of the N variant of the 802.11 Wi-Fi standard.
Wireless networking introduces a unique set of security threats that must be taken into consideration. First and foremost, the data transmitted over a wireless network is not confined to the cables concealed under floor boards, within wall cavities and false ceilings. Instead the data is quite literally traveling through the air waves. This means that anyone within range of the signal transmissions has the potential to intercept the data. In fact, placing a wireless device behind a firewall essentially renders the firewall impotent. The firewall will only block unwanted intrusion coming into the firewall via the physical connection to the internet. Compromising the wireless network from outside the building effectively bypasses the firewall.
A number of techniques are available to provide at least some level of security to wireless networks. One standard is Wired Equivalent Privacy (WEP) which was initially intended to provide a level of security for wireless networks which was at least as secure as a wired network. WEP relies on encryption to prevent the easy interception of wireless data by eavesdroppers. Encryption is RC4 based using shared 40-bit or 128-bit encryption keys. Unfortunately both levels of encryption have been proven to be breakable. That said, WEP is better than no protection at all, and if it is your only option be sure to choose the highest level of encryption.
An improved wireless encryption and authentication standard is called Wi-Fi Protected Access (WPA and WPA2). WPA data is encrypted using the RC4 stream cipher, (both 128-bit key and 48-bit) together with keys which dynamically change as the system is operational. WPA is considered to be considerably more secure than the WEP standard.
Most wireless access points also provide MAC address filtering, accepting only data from devices with a MAC address which matches a pre-defined list of trusted devices. Once again the ability to fake the IP address of many systems increases the chances that a rogue system can be made to masquerade as a trusted system.
Just like routers and switches, wireless access points provide support for remote administration. Strict password selection enforcement and secure communications must always be used when accessing the access point's administration interfaces.
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