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  • Practice a layered approach to security, with firewalls being just one, albeit fundamental, role in your security strategy. They do stop a good number of attacks, and make out jobs more defined. For example when you open holes in your firewall pay special attention to which services and machines those hole correspond to. Patch those holes first, make certain your Intrusion Detection system is monitoring those services, and if you can help it make sure those services use secure protocols and strong authentication. Firewalls are just like other systems, they have security holes themselves, yet another reason why they should not be your first line of defense. By far the greatest downfall of firewalls is the human factor. When a firewall fails to do its job its most likely due to the firewall administrator not paying attention or not following the proper firewall guidelines. Always test the rules you put in place and audit your firewall rules on a regular basis, making sure that you are really blocking what you think you are blocking.
  • The DMS is a powerful concept when implemented correctly. Firewall collect a large amount of useful information and can provide an early warning service. Firewalls are targets just like your systems, and should be configured accordingly. Many management protocols are weak when it comes to security, and VPN is one way to counteract this.
  • The DMZ (or DeMilitarized zone) is a zone or area off of your firewall that is separate from your local network. Machines that need to communicate with the Internet (i.e. web servers, ftp servers) are usually placed here. There is a separate firewall policy that protects the DMZ.
  • Only allow the services that are required. This example is a pretty easy one, HTTP and HTTPS are used for web communications and run on TCP ports 80 and 443. Sometimes you may have to open an application to the Internet that is not well documented, making the task of determining which ports to open all that more difficult.
  • If your web server is compromised you don’t want it to start attacking your local network. The DMZ configuration allows you to contain the vulnerable servers, and prevent a compromise from spreading. Also, you must allow the local network to connect to the web server, using a secure protocol such as SSH. This one may take some convincing of you developers and systems administrators. In all reality your web servers do not need to connect out to the Internet . If one becomes compromised the first thing an attacker is going to do is download some malicious code (root kit, backdoor, sniffer, etc..). You can prevent this by not letting you web server connect to the Internet. This makes patching a little more difficult. Patches must be downloaded by another system, then copied to the web server. Numerous attacks have been (and many could have been) prevented if this simple rule was in place.
  • Firewalls have the ability to provide valuable information in the form of logs. It is important to review these logs on a regular basis to see who is trying to penetrate your network and how. Portscanning is more than just noise. Many people ask after they have been compromised, “How did they find my server”. The answer is portscanning, so be aware of your environment and know what people are looking for. Certain rules provide more useful information, such as the rule that logs traffic from the DMZ to your network. This is a low traffic rule that should be monitored closely.
  • We have approximately 90mb/s of Internet bandwidth, with plans for more. We are scanned hundreds of times per day. The logs from just a few weeks of traffic contains over 30,000 packets. So how do we make this data work for use? If there is only time to secure one application this week, choose the one people are actively scanning for, not the one that has no known exploit. Zero-Day attacks happen, but it is more likely that you will be compromised with an older vulnerability. Sometime portscans are down right intrusive, so don’t be afraid to block them for a while (a few hours, a day, a week) until the scanning stops.
  • If a server in the DMZ attempts to connect to the Internet, or even worse to your local network, you want to be notified ASAP. Email is a great way to do that.
  • Firewall

    1. 1. Firewall Ir. Risanuri Hidayat, M.Sc. Teknik Elektro FT UGM POS SATPAM Firewall
    2. 2. Apa itu firewall <ul><li>Firewall adalah suatu mekanisme, sehingga suatu client dari luar dilarang/dibolehkan mengakses ke dalam jaringan (atau client yang berada di dalam dilarang/dibolehkan mengakses keluar jaringan) berdasarkan aturan-aturan yang ditetapkan. </li></ul><ul><li>Seperti pos satpam di suatu instansi/perumahan </li></ul><ul><li>Bekerja di layer: antara 3 dan 4 (bahkan 5) di TCP/IP Model </li></ul>
    3. 3. Istilah-istilah <ul><li>Masquerading </li></ul><ul><ul><li>Allows many machines to use the appear to come from the same IP address </li></ul></ul><ul><ul><li>Connections can only be initiated by internal host </li></ul></ul><ul><li>NAT – Network Address Translation </li></ul><ul><ul><li>The term “NAT” can mean many different things, see RFC2663 for details </li></ul></ul><ul><ul><li>Generally some router-level mapping and conversion between a set of private IP addresses and a single public IP address (IP Masq) or set of public IP addresses. </li></ul></ul>
    4. 4. Mengapa butuh <ul><li>To implement your policy! </li></ul><ul><li>To manage the risks of providing your services. </li></ul><ul><li>To segregate networks with different policies. </li></ul><ul><li>To provide accountability of network resources. </li></ul><ul><li>Firewalls mitigate risk </li></ul><ul><li>Blocking MOST threats </li></ul><ul><li>They have vulnerabilities as well </li></ul><ul><li>Improper configuration is the largest threat </li></ul>
    5. 5. Cara kerja <ul><li>Dengan meneliti paket-paket yang lewat firewall itu dan mencocokkannya dengan melihat daftar/aturan yang diberikan kepadanya. </li></ul><ul><li>Firewalls block certain traffic, while allowing other traffic to pass. </li></ul><ul><li>Different types of firewalls pass traffic using different methods </li></ul><ul><ul><ul><li>Packet Filtering </li></ul></ul></ul><ul><ul><ul><li>Proxy </li></ul></ul></ul><ul><ul><ul><li>Connection State Analysis </li></ul></ul></ul>Firewall Boleh lewat mbak ? Nih surat-suratnya Anak kecil ga boleh keluar.. sudah malam
    6. 6. Ada dua tipe utama <ul><li>Firewalls rules are created to match policy </li></ul><ul><li>Rules are based on: </li></ul><ul><ul><li>Routing based filters (Who – siapa) </li></ul></ul><ul><ul><ul><li>Sender and Destination </li></ul></ul></ul><ul><ul><ul><li>berasal dari mana ? </li></ul></ul></ul><ul><ul><ul><li>Mau ke mana ? </li></ul></ul></ul><ul><ul><ul><li>Tidak peduli mau ngapain di sana </li></ul></ul></ul><ul><ul><li>Content based filters (What – mau apa) </li></ul></ul><ul><ul><ul><li>TCP/IP Port numbers and Services </li></ul></ul></ul><ul><ul><ul><li>Apa yang akan kamu lakukan di sana ? </li></ul></ul></ul><ul><ul><ul><li>Tidak semudah yang nomer 1, sebab kadang-kadang bisa ditipu seorang client </li></ul></ul></ul>
    7. 7. Dua pendekatan aturan <ul><li>Default allow </li></ul><ul><ul><li>Mengijinkan semua lewat kecuali yang terdaftar </li></ul></ul><ul><ul><li>Place roadblocks/watch gates along a wide open road. </li></ul></ul><ul><li>Default deny </li></ul><ul><ul><li>Semua dilarang lewat kecuali yang terdaftar </li></ul></ul><ul><ul><li>Build a wall and carve paths for everyone you like. </li></ul></ul>
    8. 8. Packet Filtering <ul><li>Simplest form of firewalling </li></ul><ul><li>Can often be implemented on network equipment (routers, switches) </li></ul><ul><li>Blocks certain TCP/IP Ports, protocols, and/or addresses. </li></ul><ul><li>Rules are applied to the headers of the packets </li></ul><ul><li>Contoh: iptables,ipchains (Linux) </li></ul>
    9. 9. Packet Filtering <ul><li>Advantages of Packet Filtering </li></ul><ul><ul><li>High Performance </li></ul></ul><ul><ul><li>Can usually be applied to current routers/switches (No additional equipment!) </li></ul></ul><ul><ul><li>Effective </li></ul></ul><ul><li>Disadvantages of Packet Filtering </li></ul><ul><ul><li>Can quickly become a very complex configuration </li></ul></ul><ul><ul><li>Easy to misconfigure </li></ul></ul><ul><ul><li>Difficult to configure for dynamic protocols (like FTP) </li></ul></ul><ul><ul><li>Can’t do any content-based filtering (remove e-mail attachments, javascript, ActiveX) </li></ul></ul>
    10. 10. Contoh Packet Filtering <ul><li>An abbreviated packet… </li></ul><ul><li>Source SrcPort Destination DestPort </li></ul><ul><li> 8104 31337 </li></ul><ul><li>A Cisco packet filter </li></ul><ul><li>access-list 2640 deny any gt 1023 </li></ul>
    11. 11. Proxy <ul><li>Firewall accepts requests, and executes them in behalf of the user </li></ul><ul><ul><li>I want to see http:// </li></ul></ul><ul><ul><li>Firewall gets http:// content </li></ul></ul><ul><ul><li>Firewall sends content to requester </li></ul></ul><ul><li>Contoh: Squid </li></ul>
    12. 12. Proxy <ul><li>Advantages of Proxy Firewall </li></ul><ul><ul><li>They don’t allow direct connections between internal and external hosts </li></ul></ul><ul><ul><li>Can support authentication, ‘classes’ of users </li></ul></ul><ul><ul><li>Can allow/deny access based on content </li></ul></ul><ul><ul><li>Can keep very detailed logs of activity (including the data portions of packets) </li></ul></ul><ul><ul><li>Caching </li></ul></ul>
    13. 13. Proxy <ul><li>Disdvantages of Proxy Firewall </li></ul><ul><ul><li>Slower than packet filter firewalls </li></ul></ul><ul><ul><li>Require additional hardware </li></ul></ul><ul><ul><ul><li>more hardware for more users </li></ul></ul></ul><ul><ul><ul><li>slow hardware = slow service </li></ul></ul></ul><ul><ul><li>Some firewalls require special client configurations on the workstations. </li></ul></ul><ul><ul><li>Some protocols may not be supported (AIM, RealAudio, Napster, H.323) Varies by vendor. </li></ul></ul><ul><ul><li>Configuration can be complex </li></ul></ul><ul><ul><ul><li>Must configure proxy for each protocol </li></ul></ul></ul>
    14. 14. Connection State Analysis <ul><li>Similar to packet filtering, but analyzes packets to make sure connection requests occur in the proper sequence. </li></ul><ul><li>Example: </li></ul><ul><ul><li>ICMP Echo Replies are not accepted through the firewall unless there is an outstanding ICMP Echo Request. </li></ul></ul>
    15. 15. Connection State Analysis <ul><li>Advantages </li></ul><ul><ul><li>Caching </li></ul></ul><ul><ul><li>Content Monitoring </li></ul></ul><ul><li>Disadvantages </li></ul><ul><ul><li>Performance </li></ul></ul><ul><ul><li>Overhead requires more expensive system </li></ul></ul>
    16. 16. Topologi <ul><li>Bridge-type firewall </li></ul><ul><ul><li>Invisible to users </li></ul></ul><ul><ul><li>Easy to install for already existing networks </li></ul></ul><ul><li>Router-type firewalls </li></ul><ul><ul><li>Has IP Address, visible to users </li></ul></ul>
    17. 17. Topologi <ul><li>Advantages of Bridge-type firewall </li></ul><ul><ul><li>Invisible to users </li></ul></ul><ul><ul><li>Easy to install for already existing networks </li></ul></ul><ul><li>Disadvantages of Bridge-type firewall </li></ul><ul><ul><li>Requires more equipment than packet filtering </li></ul></ul><ul><ul><li>Rules may be more confusing to configure </li></ul></ul><ul><li>Advantages of Router-type firewall </li></ul><ul><ul><li>Rule configuration slightly better than bridge </li></ul></ul><ul><li>Disadvantages of Router-type firewall </li></ul><ul><ul><li>System is ‘visible’ to users and outsiders </li></ul></ul>
    18. 18. Problems <ul><li>Firewalls as filters can be considered for most part to be infallible... but as a security measure? They can only enforce rules (generally static) </li></ul>internet Firewall
    19. 19. Problems <ul><li>“Crunchy on the outside, but soft and chewy on the inside.” </li></ul>internet Jaringan kita Jaringan terpercaya Firewall
    20. 20. Setting Firewall <ul><li>Using the “DMZ” (DeMilitarized zone) to your advantage </li></ul><ul><li>Firewalls as Intrusion Detection devices </li></ul><ul><li>Configure VPN’s for management </li></ul>
    21. 21. DMZ Configuration <ul><li>Separate area off the firewall </li></ul><ul><li>Different network segments may have different policies </li></ul><ul><ul><li>Departments </li></ul></ul><ul><ul><li>Service areas </li></ul></ul><ul><ul><li>Public Services </li></ul></ul><ul><ul><li>Internal Services </li></ul></ul><ul><li>Usually a different subnet </li></ul><ul><li>Commonly used to house Internet facing machines (i.e. Web Servers) </li></ul><ul><li>Has its own firewall policy </li></ul>
    22. 22. DMZ Configuration <ul><li>Place web servers in the “DMZ” network </li></ul><ul><li>Only allow web ports (TCP ports 80 and 443) </li></ul>internet Firewall Web Server
    23. 23. DMZ Configuration <ul><li>Don’t allow web servers access to your network </li></ul><ul><li>Allow local network to manage web servers (SSH) </li></ul><ul><li>Don’t allow servers to connect to the Internet </li></ul><ul><li>Patching is not convenient </li></ul>Firewall Web Server internet Mas ..yang merah gak boleh lewat lho
    24. 24. DMZ Configuration Firewall Web Server <ul><li>Jaringan Lokal: </li></ul><ul><li>Semua boleh menghubungi web-server (port 80/443 </li></ul><ul><li>PC-PC tertentu boleh menghubungi server lewat SSH (port 22) </li></ul><ul><li>Server tidak boleh menghubungi jaringan lokal </li></ul><ul><li>Internet: </li></ul><ul><li>Semua boleh menghubungi web-server (port 80/443 </li></ul><ul><li>Selain layanan web tidak diperkenankan </li></ul><ul><li>Server tidak boleh jalan-jalan di internet </li></ul>
    25. 25. Firewall sebagai IDS <ul><li>IDS = Intrusion Detection System </li></ul><ul><li>Collect log information from the deny rules </li></ul><ul><li>Find Portscanning, hacking attempts, etc… </li></ul><ul><li>Isolate traffic with deny rules helps cut down the information overload </li></ul>
    26. 26. Firewall sebagai IDS <ul><li>What to do with ALL that data…..Graph It! </li></ul><ul><li>Shows trends, what people are looking for </li></ul><ul><ul><li>Helps prioritize security tasks </li></ul></ul><ul><li>Occasionally you may want to block portscans </li></ul>
    27. 27. Firewall sebagai IDS <ul><li>Pay close attention to traffic leaving DMZ </li></ul><ul><li>Often the first sign of a compromise </li></ul><ul><li>Low traffic rules, so logs aren’t as enormous </li></ul><ul><li>Email is nice, provided you’re the only one reading it </li></ul>
    28. 28. VPN <ul><li>VPN = Virtual Private Network </li></ul><ul><li>VPN is far more secure than other management methods: </li></ul><ul><ul><li>SSL and SSH are vulnerable to Man-In-The Middle Attacks </li></ul></ul><ul><ul><li>Telnet and SNMP are clear text </li></ul></ul><ul><ul><li>There are no known MIM attacks against IPSEC (Yet) </li></ul></ul>
    29. 29. VPN <ul><li>VPN clients are supported on most platforms </li></ul><ul><li>Most firewalls will work with most clients </li></ul><ul><li>Netscreen now officially supports FreeSwan </li></ul><ul><li>Mac OS X is now supporting VPN </li></ul>
    30. 30. Conclusions <ul><li>People don’t just put up a thick front door for their sensitive belongings, you shouldn’t for your network either. </li></ul><ul><li>Firewalls are an effective start to securing a network. Not a finish. </li></ul><ul><li>Care must be taken to construct an appropriate set of rules that will enforce your policy. </li></ul>