Cyberdefense Technologies
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Presentation Transcript
Cyberdefense Technologies Firewalls Intrusion detection And beyond
Defensive Strategy • Deceive the attacker • Frustrate the attacker • Resist the attacker • Recognize and Respond to the attacker
Security Desires • Logging of successful connections, rejected packets and suspected attacks • Immunity to Denial of Service attacks • Protection against information gathering probes
Defenses against DOS • The best defense against DDos attacks is to prevent initial system compromises • However, even vigilant hosts can become targets because of lesser prepared, less security aware hosts • It is difficult to specifically defend against becoming the ultimate target of a DDos attack but protection against being used as a daemon or master system is more easily attainable
Ingress Filtering • Ingress filtering manages the flow of traffic as it enters a network under your administrative control • Servers are typically the only machines that need to accept inbound connections from the public Internet • Ingress filtering can be performed at the border to prohibit externally initiated inbound connections to non-authorized services
Egress Filtering • Egress filtering manages the flow of traffic as it leaves a network under your administrative control • Egress filtering from sources like university campuses can make a difference • Egress filtering alone does not provide a complete solution to the problem
Firewalls • Defensive “middle ground” between public and protected network • The demands from a firewall can differ significantly • An internal network, where a balance has to be found between what can come in and out, a website publicly accessible or a virtual Private Network pose very different problems
Firewalls are for policy control • They permit a site’s administrator to set a policy on external access • Just as file permissions enforce an internal security policy, a firewall can enforce an external security policy
Firewall Technologies • Network Address Translation (NAT) • Most use packet filtering rules to determine packet access • Some use “stateful inspection” to manage connections • Some application proxy support • A few allow custom proxy creation *BONUS*
Static Packet Filtering • Uses information in Packet headers: • Destination IP address • Source IP subnet • Destination service Port • Information compared with Access Control List (ACL) • Flag (TCP): stop Anything with SYN=1, but port scanners can choose to have ACK=1,FIN=1, all other flags set to 0… • Flag Not an option with UDP
Internet router is blocking tcp/udp ports 135-139 Firewall allows only outbound http (80) and smtp (25) traffic Example Attack Hacker’s Objective:Gain control of internal NT server from Internet
Dynamic Packet Filtering (Stateful Inspection) • Acts on the same principle as Static Packet Filtering, but maintains a connection or “state” table in order to monitor communication session • Less easy to abuse • Filtering hard to configure to full satisfaction and reduces router’s performance
Problems with Firewalls • Conventional firewalls rely on the notions of restricted topology and control entry points to function • Everyone on one side of the firewall is to be trusted • Anyone on the other side is potentially an enemy • “extranets” can allow outsiders to reach the “inside” of the firewall • Some machines need more access to the outside than do others • End-to-end encryption: firewalls generally do not have the necessary keys to inspect traffic • Log review, software currency, … (high maintenance)
Distributed Firewalls • In such a scheme, policy is still centrally defined; enforcement, however, takes place on each endpoint • Helps control trust issues
What are Honeypots? • Honeypots are one of the methods used in intrusion detection • Setup a "decoy" system • Non-hardened operating system • Appears to have several vulnerabilities • Similar configuration to production • Fake content • Deceive intruder for alert and study
Attracting Blackhats • What do you do to attract blackhats to your Honeypot? • Absolutely nothing, that is the scary part. You have to sit back and wait. • The blackhat community is extremely aggressive, you would be surprised at what they will find.
Honeypot as attack host • Once compromised, can't the bad guys use one of your honeypots to attack someone else? • That risk exists ! • use several layers of access control devices that limit and control what type of outbound connections are allowed, and how many
The Honeynet project • Distributed team of security experts • Hardware to capture and analyze intruder activity • Evolving honeypot technology and attack analysis
What’s wrong with honeypots? • The insurance model will not allow you to take unnecessary risks without a substantial increase in premium • Risk management says that honey pots increase risk for demonstrably invalid reasons • You can learn more by using better instrumentation • Transient effectiveness
Transient Effectiveness • The threat reality is that most attackers are morons and will attack with DoS if denied real access • Honey pots must be kept up to date but in general aren’t • Honey pots must act like the host operating system • Fix current problems rather than generating new ones
Too many hosts to secure • Virtually all operating systems and network devices are insecure out of the box • This must change • Operating systems maintained by normal users must be set to take care of themselves by default • Growth of the net will be the single largest factor as to why there are so many vulnerable systems • It is unrealistic to assume that the net will ever be safe
Where does IDS fit? • IDS are useful as an additional layer of defense, no more • IDS are not helpful when advanced attackers are attacking you with new attacks • Two major types today: network IDS (snort) and host IDS (AIDE, log watcher, etc) • Missing IDS type: application IDS • High false alarm rates (wasted admin time)
IDS and Policy • Security Policy is the first step (defining what is acceptable and what is being defended) • Notification • Who, how fast? • Response Coordination
Jane did a port sweep! NMAP
Honeypot (Deception System) Generic Server (Host-Based ID) (Snort 2.0) Internet Firewall (Perimeter Logs) Filtering Router (Perimeter Logs) Statistical IDS (Snort) Network IDS (Snort) IDS Implementation Map
Detection Engine • Rules form “signatures” • Modular detection elements are combined to form these signatures • Wide range of detection capabilities • Stealth scans, OS fingerprinting, buffer overflows, back doors, CGI exploits, etc. • Rules system is very flexible, and creation of new rules is relatively simple
Learning More • www.snort.org • Writing Snort Rules • www.snort.org/snort_rules.html • FAQ, USAGE file, README file, man page • Snort mailing lists • Books • Intrusion Detection: An Analysts Handbook by Northcutt • Intrusion Signatures and Analysis by Northcutt • The Practical Intrusion Detection Handbook by Paul Proctor
But What Slips Through? • Signatures based on traffic model • Attacks stay with same source IP set • Signature assume fixed characteristics • Packets involving attack stay with similar content • Signature assume obvious distinction from legitimate traffic • What is legitimate is never malicious
How do We Catch the Slips? • Non-signature based collection • Short-term (hours, max) packet collection, rotating -> libpcap • Medium-term (weeks, max) headers+content summary -> expanded flow • Long-term (years) headers+sizes -> flow • Privacy concerns • Efficiency concerns • Sampling concerns
What can You Do with Just Flows? • Indicative, not probative • Time-series, with departures • DDoS ramp-up • Scanning: worms/virus • Threashold violations • Spam vs. email • Streaming media vs. web browsing • Locality violations • Malware beaconing • Worms/virus • Spyware
Automated Response • Ongoing work • Local indicators fused to alert • Firewalls/IDS exchange intrusion information • IODEF standard • Dynamically alter firewall rules • Dynamically alter routing tables to reconfigure network
Frustrate Deceive Recognize Respond Layered Defenses Source: Shawn Butler, Security Attribute Evaluation Method Goal 1 Goal 8 Goal 2 Goal 7 Goal 3 Goal 6 Goal 5 Goal 4
