Top Kodi Archive and Support File Vintage Software APK MS-DOS CD-ROM Software CD-ROM Software Library Software Sites Tucows Software Library Shareware CD-ROMs Software Capsules Compilation CD-ROM Images ZX Spectrum DOOM Level CD. Books to Borrow Open Library. Featured All Books All Texts This Just In Smithsonian Libraries FEDLINK US Genealogy Lincoln Collection. Top American Libraries Canadian Libraries Universal Library Project Gutenberg Children's Library Biodiversity Heritage Library Books by Language Additional Collections. Featured All Video This Just In Prelinger Archives Democracy Now! Occupy Wall Street TV NSA Clip Library. Search the Wayback Machine Search icon An illustration of a magnifying glass.

Mobile Apps Wayback Machine iOS Wayback Machine Android Browser Extensions Chrome Firefox Safari Edge. Archive-It Subscription Explore the Collections Learn More Build Collections. Sign up for free Log in. Search metadata Search text contents Search TV news captions Search radio transcripts Search archived web sites Advanced Search. remove-circle Internet Archive's in-browser video player requires JavaScript to be enabled. It appears your browser does not have it turned on. Please see your browser settings for this feature. remove-circle Share or Embed This Item. EMBED for wordpress. com hosted blogs and archive. Want more? Advanced embedding details, examples, and help! Addeddate Identifier comp-tia-security-sysycomplete-course-exam Ocr tesseract 5. plus-circle Add Review. There are no reviews yet. Be the first one to write a review. download 2 files. download 1 file. Firewall logs should be the first thing you check when an intrusion has been detected. You should know how to access the logs and how to read them.

Look at the blocked Gnutella packet that is pointed out. I know it is a Gnutella packet because the inbound port on my firewall that the external computer is trying to connect to shows as port ; this associates with Gnutella. Gnutella is an older P2P file- sharing network. None of the computers on this particular network use or are in any way connected to the Gnutella service. These external computers are just random clients of the Gnutella P2P network trying to connect to anyone possible. To eliminate that IP, you could add it to an inbound filter or to an ACL. So far, we have discussed host-based firewalls in Chapter 3 and, just now, network- based firewalls. However, both of these firewalls can also fall into the category of application firewall. If either type runs protocols that operate on the application layer of the OSI model, then it can be classified as an application firewall. That means that it can control the traffic associated with specific applications.

Many host-based firewalls fall into this category, but when it comes to network-based firewalls, it varies. A basic SOHO router with built-in firewalling capabilities would usually not fall into the application firewall category. However, more advanced network appliances from companies such as Bar- racuda, Citrix, Fortinet, and Smoothwall do fall into this category. This means that they allow for more in-depth monitoring of the network by controlling the input, output, and access to applications and services all the way up through the application layer of the OSI model. These appliances might also be referred to as network-based application layer firewalls.

Going a step further, some of the aforementioned network appliances have tools that are designed to specifically protect HTTP sessions from XSS attacks and SQL injection. These types of tools are known as web application firewalls. WAFs can help to protect the servers in your environment. NOTE A firewall appliance needs more than one network adapter so that it can con- nect to more than one network; this is known as a multihomed connection. It might be dual-homed two adapters , or perhaps it has more, maybe three network adapters, in case you want to implement a DMZ or another perimeter security technique. Firewalls are often considered to be all-in-one devices, but actually they provide specific functionality as discussed in this section.

Still, it is common to hear people refer to a firewall when they are really talking about another technology, or even another device. For example, many SOHO users have an all-in-one multifunction network device. This device has four ports for wired connections, plus a wireless antenna; it connects all the computers to the Internet, and finally has a firewall built-in. Because some users consider this to be simply a firewall, you should teach them about the benefits of disabling SSID broadcasting, and enabling MAC filter- ing. By disabling Service Set Identifier SSID broadcasting, the average user cannot connect wirelessly to the device. An attacker knows how to bypass this, but it is an important element of security that you should implement after all trusted computers have been connected wirelessly.

Chapter 8: Network Perimeter Security Proxy Servers A proxy server acts as an intermediary for clients, usually located on a LAN, and the servers that they want to access, usually located on the Internet. By definition, proxy means go-between, or mediator, acting as such a mediator in between a private network and a public network. The proxy server evaluates requests from clients and, if they meet certain criteria, forwards them to the appropriate server. For example, a basic four-port router can act as an IP proxy for the clients on the LAN it protects. An IP proxy can be the victim of many of the network attacks mentioned in Chapter 6, especially DoS attacks. Regardless of whether the IP proxy is an appliance or a com- puter, it should be updated regularly, and its log files should be monitored periodically and audited according to organization policies. Although there are FTP and SMTP proxies, among others, the most common caching proxy is the HTTP proxy, also known as a web proxy, which caches web pages from servers on the Internet for a set amount of time.

Examples of caching proxies include WinGate for Windows systems and Squid commonly used on Linux-based systems. An example of a caching proxy is illustrated in Figure com, and that she was the first person to do so on the network. When another person on your network Client B makes a subsequent request for www. Most HTTP proxies check websites to verify that nothing has changed since the last request. Because information changes quickly on the Internet, a time limit of 24 hours is common for storing cached information before it is deleted. Web browsers make use of a proxy auto-configuration PAC file, which defines how the browser can automatically choose a proxy server.

The file itself and the embedded JavaScript function pose a security risk in that the file can be exploited and modified, ultimately redirecting the user to unwanted and poten- tially malicious websites. Consider disabling PAC files and auto-configuration in general within client web browsers. Client A HTTP Proxy Web Server Subsequent request goes to the HTTP proxy only. One device or computer might do all these things or just one or two. It depends on the software used or appliance installed. This is done when users on the Internet are accessing server resources on your network.

Generally, a proxy server has more than one network adapter so that it can connect to the various net- works it is acting as a mediator for. Each of the network adapters in a proxy should be periodically monitored for improper traffic and for possible network attacks and other vulnerabilities. A proxy server might be the same device as a firewall, or it could be separate. Because of this, a multitude of network configurations are pos- sible. Proxy servers, especially HTTP proxies, can be used maliciously to record traffic sent through them; because most of the traffic is sent in unencrypted form, this could be a security risk. A possible mitigation for this is to chain multiple prox- ies together in an attempt to confuse any onlookers and potential attackers. Most often, a proxy server is implemented as a forward proxy. This means that clients looking for websites, or files via an FTP connection, pass their requests through to the proxy.

However, there is also a reverse proxy, where multiple HTTP or FTP servers use a proxy server and send out content to one or more clients. These HTTP and FTP servers could be located in a server farm or similar grouping, and the reverse proxy might also undertake the role of load balancer in this situation. However, it could be that you have a single application stored on sev- eral servers. Those servers can work together utilizing clustering technology. The clustering might be controlled by the servers themselves or, more commonly, a load balancer can be installed in front of the servers that distributes the network load among them. That load balancer in effect acts as a reverse proxy. But in some cases, you might need a proxy that does not modify requests. This is known as a transparent proxy. While it allows for increased efficiency, there is less protection for the client system. Another example of a proxy in action is Internet content filtering. An Internet con- tent filter, or simply a content filter, is usually applied as software at the application layer and can filter out various types of Internet activities such as websites accessed, e-mail, instant messaging, and more.

It often functions as a content inspection device, and disallows access to inappropriate web material estimated to be a big per- centage of the Internet! Internet content filters can be installed on individual clients, but by far the more efficient implementation is as an individual proxy that acts as a mediator between all the clients and the Internet. These proxy versions of content filters secure the network in two ways: one, by forbidding access to potentially mali- cious websites, and two, by blocking access to objectionable material that employees might feel is offensive. It can also act as a URL filter; even if employees inadver- tently type an incorrect URL, they can rest assured that any objectionable material will not show up on their display. Internet filtering appliances analyze just about all the data that comes through them, including Internet content, URLs, HTML tags, metadata, and security certificates such as the kind you would automatically receive when going to a secure site that starts with https.

However, revoked certificates and certificate revocation lists, or CRLs, will not be filtered because they are only published periodically. Another similar appliance is the web security gateway. Web security gateways such as Forcepoint, previously known as Websense act as go-between devices that scan for viruses, filter content, and act as data loss prevention DLP devices. As you can see, many, many options for security devices are available for your net- work, and many vendors offer them. NOTE Proxies, content filters, and web security gateways are examples of servers that probably face the Internet directly. The two most important security controls are to keep the application up to date, and to review and apply vendor-provided hardening documentation. Remember to do these things before putting the proxy server or other Internet-facing servers in a live environment. Honeypots and Honeynets Honeypots and honeynets attract and trap potential attackers to counteract any attempts at unauthorized access of the network.

This isolates the potential attacker in a monitored area and contains dummy resources that look to be of value to the perpetrator. While an attacker is trapped in one of these, their methods can be studied and analyzed, and the results of those analyses can be applied to the general security of the functional network. A honeypot is generally a single computer but could also be a file, group of files, or an area of unused IP address space, whereas a honeynet is one or more computers, servers, or an area of a network; a honeynet is used when a single honeypot is not sufficient. Either way, the individual computer, or group of servers, will usually not house any important company information. Various analysis tools are implemented to study the attacker; these tools, along with a centralized group of honeypots or a honeynet , are known collectively as a honeyfarm. One example of a honeypot in action is the spam honeypot. It might ultimately keep the spammers away from the real e-mail addresses, because the spammers are occupied elsewhere.

A spam honeypot could be as simple as a single e-mail address or as complex as an entire e-mail domain with multiple SMTP servers. Of course, as with any technology that studies attackers, honeypots also bear risks to the legitimate network. Chapter 8: Network Perimeter Security Often, honeypots and honeynets are used as part of a more complex solution known as a network intrusion detection system, discussed following a short review of data loss prevention. Data Loss Prevention DLP We mentioned DLP in Chapter 3. Data loss prevention DLP systems are designed to protect data by way of content inspection.

They are meant to stop the leakage of confidential data, often concentrating on communications. As such, they are also referred to as data leak prevention DLP devices, information leak prevention ILP devices, and extrusion prevention systems. Regardless, they are intended to be used to keep data from leak- ing past a computer system or network and into unwanted hands. In network-based DLP, systems deal with data in motion and are usually located on the perimeter of the network. Network-based DLP systems can be hardware-based or software-based. An example of a network-based DLP system would be one that detects and prevents the transfer of confidential e-mail information outside the net- work.

Organizations such as Check Point offer DLP solutions, and there are some free open source applications as well. Going further, there are cloud-based DLP solutions available. But it all depends on where you store your data. If you store some or all of your data on the cloud, or if you have a large bring your own device BYOD or choose your own device CYOD population, then cloud-based DLP becomes an important part of your security strategy. Because the data—and the security of that data—is now external from the company, planning becomes even more vital. Some key elements of the security mindset include: 1 planning for the mitigation of security risks; 2 adequate understanding of the cloud-based provider, where and how data is stored, and their service-level agreement SLA ; 3 in-depth analysis of code and the types of data that will be stored in the cloud; and 4 strong authentication, auditing, and logging.

Leaks can still occur due to poor implementation of DLP systems, so it is essential to plan what type of DLP solution your organization needs, exactly how it will be installed, and how it will be monitored. Although a great many attacks can hamper an individual computer, just as many network attacks could pos- sibly take down a server, switch, router, or even an entire network. Network-based IDSs were developed to detect these malicious network attacks, and network-based IPSs were developed in an attempt to prevent them. NIDS A network intrusion detection system NIDS by definition is a type of IDS that attempts to detect malicious network activities, for example, port scans and DoS attacks, by constantly monitoring network traffic.

It can also be instrumental in rogue machine detection, including rogue desktops, laptops, and mobile devices, as well as rogue access points, DHCP servers, and network sniffers. A NIDS should be situated at the entrance or gateway to your network. It is not a firewall but should be used with a firewall. Because the NIDS inspects every packet that traverses your network, it needs to be fast; basically, the slower the NIDS, the slower the network. Figure illustrates how a NIDS might be implemented on a network. Often it is placed in front of a firewall. The NIDS detects attacks and anomalies and alerts the administrator if they occur, whereas the firewall does its best to prevent those attacks from entering the network. However, a NIDS could be placed behind the firewall, or you might have multiple NIDS points strategically placed around the network.

If the NIDS is placed in front of the firewall, it generates a lot more administrator alerts, but these can usually be whittled down within the firmware or software of the device running the NIDS. Regardless of where the NIDS is located, a network administrator should monitor traffic from time to time; to do so, the computer, server, or appliance that has the NIDS installed should have a network adapter configured to work in promiscuous mode. This passes all traffic to the CPU, not just the frames addressed to it. A couple of disadvantages of a NIDS, aside from possible network performance issues, are that it might not be able to read encrypted packets of infor- mation and will not detect problems that occur on an individual computer. There- fore, to secure a network and its hosts, many organizations implement a mixture of NIDS and HIDS. If a NIDS is placed in front of the firewall, it is subject to attack; therefore, it should be monitored and updated regularly.

Some NIDS solutions will auto-update. Finally, the biggest disadvantage of a NIDS is that it is passive, mean- ing it only detects attacks; to protect against, or prevent, these attacks, you need some- thing active, you need a NIPS. NIPS A network intrusion prevention system NIPS is designed to inspect traffic and, based on its configuration or security policy, either remove, detain, or redi- rect malicious traffic that it becomes aware of. The NIPS as well as the NIDS is considered to be an application-aware device, meaning it can divine different types of packets, define what application they are based on, and ultimately permit or disallow that traffic on the network. More and more companies are offering NIPS solutions in addition to, or instead of, NIDS solutions.

Not only can a NIPS go above and beyond a NIDS by removing or redirecting malicious traffic, it can also redirect a recognized attacker to a single computer known as a padded cell, which contains no information of value and has no way out. Like a NIDS, a NIPS should sit inline on the network, often in front of the fire- wall, although it could be placed elsewhere, depending on the network segment it protects and the network architecture. Regardless of the solution you select, as packets pass through the device, they are inspected for possible attacks. These devices need to be accurate and updated often hopefully automatically to avoid the misidenti- fication of legitimate traffic, or worse, the misidentification of attacks.

If the NIPS blocks legitimate traffic, it would be known as a false positive, and effectively could deny service to legitimate customers, creating a self-inflicted denial-of-service of sorts. Many IPS systems can monitor for attack signatures and anomalies. To protect against this, some devices have the capability to hide or mask their IP address. They might also come with an internal firewall. It is also important to select an IPS solution that has a secure channel for the manage- ment console interface. One advantage of newer NIPS solutions is that some of them can act as protocol analyzers by reading encrypted traffic and stopping encrypted attacks.

In general, the beauty of a NIPS compared to a host-based IPS HIPS is that it can protect non-computer-based network devices such as switches, routers, and firewalls. How- ever, the NIPS is considered a single point of failure because it sits inline on the network. Due to this, some organizations opt to install a bypass switch, which also enables the NIPS to be taken offline when maintenance needs to be done. A vital NIPS consideration is whether to implement a fail-close or fail-open policy—in essence, deciding what will happen if the NIPS fails. Fail-close means that all data transfer is stopped, while fail-open means that data transfer includ- ing potential attacks are passed through. Say that the NIPS was protecting an individual server or router , and had a certain level of control over that system. In a fail-close scenario, it would disconnect the system that it is protecting, stopping all data transfer. This is unacceptable to some organizations that require near percent uptime.

These organizations are willing to accept additional risk, and therefore are more recep- tive to a fail-open scenario. Sometimes, fail-open scenarios are necessary. For instance, you might opt to have a firewall filter the bulk of traf- fic coming into the network, but have the IPS filter only specific traffic, reducing the chances of IPS failure. This layered approach can offer greater security with less chance of attacks passing through, but often comes with increased cost and administration. Summary of NIDS Versus NIPS Table summarizes NIDS versus NIPS. Bro IDS Con: Only detects malicious activities. NIPS Detects, removes, Pro: Detects and mitigates malicious activity. Check Point detains, and Systems Pro: Can act as a protocol analyzer.

redirects traffic solutions Con: Uses more resources. Con: Possibility of false positives and false negatives. These are loaded on a computer and are con- trolled by the user in a GUI environment; they capture packets, enabling the user to analyze them and view their contents. It decodes application layer protocols, such as HTTP, FTP, or SMTP, and forwards the results to the IDS or IPS analysis engine. Then the analysis engine studies the information for anoma- lous or behavioral exploits. This type of analysis can block many exploits based on a single signature. They moni- tor the radio spectrum for unauthorized access and rogue access points. However, these names might be incorporated into the concept of NIDS and NIPS by some organizations. Regardless, be sure to use an IDS or IPS for your wired and wire- less connections! Unified Threat Management A relatively newer concept, unified threat management UTM is the culmina- tion of everything we discussed in this chapter so far.

However, with all these extra devices and technologies come added cost and more administration. And so, UTM providers simplify the whole situation by offering all-in-one devices that combine the various levels of defense into one solution. The all-in-one device might also be referred to as a next-generation firewall NGFW. Companies such as Cisco, Fortinet, and Sophos to name a few offer UTM and NGFW solutions; often this is a single device that sits last on the network before the Internet connection. They usually come with a straightforward web-based GUI, which is good news for the beleaguered security administrator who might be burning the midnight oil research- ing the latest attacks and prevention methods. Get past the UTM, and your job as an attacker is done. Secondary and backup UTM devices, as well as server-based HIDSs, strike a balance and create a certain level of defense in depth, while still retaining a level of simplicity.

Another consideration is that UTMs should be quick. If they are to take the place of several other devices, then their data processing and traffic flow requirements will be steep. It was important to discuss each of the tools and technologies separately in this chapter so that you understand how to work with each. But keep in mind that many of these technologies are consolidated into a single solution, a trend that will likely continue as we move forward. This collaborative effort makes for a strong network perimeter. The firewall is at the frontlines, whether it is part of a UTM or running as a separate device. ACLs, stateful packet inspection, and network address translation should be employed to solidify your firewall solution.

If you answered no, then prepare ye for more metaphorical expression. Remember that enemy forces are everywhere. They are lying in wait just outside your network, and they can even reside within your network—for example, the malicious insider, that dragon who has usurped the mountain and is perhaps in control of your pre- cious treasure your data. Analogies aside, this is all clear and present danger—it is real, and should be enough to convince you to take strong measures to protect your network. Often, the act of securing the network can also provide increased efficiency and pro- ductivity.

For example, a proxy server can act to filter content, and can provide ano- nymity, but also saves time and bandwidth for commonly accessed data. A honeypot can trap an attacker, thus securing the network, but the secondary result is that net- work bandwidth is not gobbled up by the powerful attacker. However, the same act can have the opposite effect. For example, a NIDS that is installed to detect anoma- lies in packets can slow down the network if it is not a powerful enough model. Just make sure it has the core processing and memory required to keep up with the amount of data that will flow through your network. If you can find the right balance of security and performance while employing your network security solution, it will be analogous to your network donning the aegis, acting as a powerful shield against network attacks from within and without.

Review Key Topics Review the most important topics in the chapter, noted with the Key Topic icon in the outer margin of the page. Table lists a reference of these key topics and the page number on which each is found. You will find a PDF con- taining the scenario and questions, and also supporting videos and simulations. Chapter 8: Network Perimeter Security Review Questions Answer the following review questions. Check your answers with the correct answers that follow. Which tool would you use if you want to view the contents of a packet? TDR B. Port scanner C. Protocol analyzer D. Loopback adapter 2. The honeypot concept is enticing to administrators because A.

It enables them to observe attacks. It traps an attacker in a network. It bounces attacks back at the attacker. It traps a person physically between two locked doors. James has detected an intrusion in his company network. What should he check first? DNS logs B. Firewall logs C. The Event Viewer D. Performance logs 4. Which of the following devices should you employ to protect your network? Select the best answer. Protocol analyzer B. Firewall C. DMZ D. Proxy server 5. Firewall B. Smartphone C. Performance Monitor D. Where are software firewalls usually located? On routers B. On servers C. On clients D. On every computer 7. Where is the optimal place to have a proxy server? In between two private networks B. In between a private network and a public network C. In between two public networks D. On all of the servers 8. A coworker has installed an SMTP server on the company firewall.

What security principle does this violate? Chain of custody B. Use of a device as it was intended C. Man trap D. Use of multifunction network devices 9. You are working on a server and are busy implementing a network intrusion detection system on the network. You need to monitor the network traffic from the server. What mode should you configure the network adapter to work in? Half-duplex mode B. Full-duplex mode C. Auto-configuration mode D. Promiscuous mode Which of the following displays a single public IP address to the Internet while hiding a group of internal private IP addresses? HTTP proxy B. Protocol analyzer C. IP proxy D. SMTP proxy E. If your ISP blocks objectionable material, what device would you guess has been implemented? Proxy server B.

Internet content filter D. NIDS Of the following, which is a collection of servers that was set up to attract attackers? DMZ B. Honeypot C. Honeynet D. VLAN Which of the following will detect malicious packets and discard them? NIDS C. NIPS D. PAT Which of the following will an Internet filtering appliance analyze? Select the three best answers. Content B. Certificates C. Certificate revocation lists D. URLs Which of the following devices would detect but not react to suspicious behav- ior on the network? Select the most accurate answer. NIPS B. NIDS D. HIDS E. One of the programmers in your organization complains that he can no longer transfer files to the FTP server.

You check the network firewall and see that the proper FTP ports are open. What should you check next? ACLs B. AV definitions D. FTP permissions Which of the following is likely to be the last rule contained within the ACLs of a firewall? Time of day restrictions B. Explicit allow C. IP allow any D. Implicit deny Which of the following best describes an IPS? A system that identifies attacks B. A system that stops attacks in progress C. A system that is designed to attract and trap attackers D. A system that logs attacks for later analysis What is a device doing when it actively monitors data streams for malicious code? Content inspection B. URL filtering C. Load balancing D. NAT Allowing or denying traffic based on ports, protocols, addresses, or direction of data is an example of what? Port security B.

Content inspection C. Firewall rules D. Which of the following should a security administrator implement to limit web-based traffic that is based on the country of origin? AV software B. Proxy server C. Spam filter D. Load balancer E. Firewall F. URL filter G. You have implemented a technology that enables you to review logs from computers located on the Internet. The information gathered is used to find out about new malware attacks. What have you implemented? Honeynet B. Firewall D. Proxy Which of the following is a layer 7 device used to prevent specific types of HTML tags from passing through to the client computer? Router B. Content filter D. Your boss has asked you to implement a solution that will monitor users and limit their access to external websites.

Which of the following is the best solution? NIDS B. Block all traffic on port 80 D. Which of the following firewall rules only denies DNS zone transfers? deny IP any any B. deny TCP any any port 53 C. deny UDP any any port 53 D. deny all dns packets Answers and Explanations 1. A TDR is a time-domain reflectometer, a tool used to locate faults in cabling. I threw that one in for fun. A loopback adapter is a device that can test a switch port or network adapter depending on how it is used.

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If on the other hand you decide that a specific type of traffic should not be granted access, you would explicitly deny that traffic within an ACL. However, with all these extra devices and technologies come added cost and more administration. NOTE Chapter 19 gives strategies for taking the exam and therefore does not map to any specific objectives. It depends on the software used or appliance installed. A firewall blocks network attacks.

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