Domain Two: Technologies and Tools Flashcards
What is a firewall ?
A firewall acts as a gatekeeper that allows traffic to a network segment based on rules that are implemented. A firewall can be hardware or software based.
How does a firewall work ?
- NAT rules
- Basic Packet Filtering
- Stateful Packet Filtering
ACLs - Application Layer Proxies
How are firewall rules read ?
Firewall rules are read top down so the best configuration is to have the explicit allows at the top and then an implicit deny which blocks everything else at the bottom of the list
What is a firewall ACL ?
Lists of users, network devices and addresses and their permitted actions. Most commonly used in file systems but ACLs can be used on any device. Rules are read from top down so the last rule should be a deny everything.
What is an application based firewall ?
Unlike basic packet filtering this is a much deeper dive into the packets. They suffer from perfomance degradation so only a choice for high value assets.
What is basic packet filtering ?
Basic Packet Filtering examines the headers only for protocol, ports and source and destination addresses and will either block or allow that traffic based on the implemented ruleset.
So the FTP protocol may be allowed at one destination but not another etc.
What is Network Address Translation ?
Network Address Translation is where there is only one exposed public ip which represents multiple private IP addresses on the network. The attacker only ever sees the external public IP address of the firewall and so this abstraction offers a degree of isolation that will be used even when IPv6 becomes the most prevalent network protocol.
Firewalls can be configured to perform NAT.
What is Stateful Packet inspection ?
Looks at the state of the packet - is this a new connection , an existing one, origin form internal or external source and then evaluated against a specific ruleset.
Another feature of stateful packet inspection is to have all ports closed until they are needed thus limiting the attackers port scanning usefulness.
What is an IDS and an IPS ?
IDS - Detect Log and Alert on unauthorised networks can be done in real time or after the fact
IPS - All of the above but it also prevents
NIDS/NIPS - Network based IDS and IPS that can detect network and host
HIDS/HIPS - Only detects host its more detailed than the above
You must also consider that these systems and subject to changes in business process etc which can lead them to generate
False Positives - Where there is a triggering of the rules but no malicious events
False Negatives - Where the rules were not triggered but the event was malicious
What is the function of the IDS analysis engine ?
This is the brains of the whole operation and responsible for the analysis of the caught traffic against the signatures in the database.
What is the function of the signature database ?
This is a collection of known patterns and definitions of malicious activity. An IDS/IPS should receive regular updates to this database as new attack patterns are recognised.
What is the traffic collector function of an IDS/IPS ?
Sometimes known as a sensor - it captures all the traffic that the IDS will analyse.
In HIDS that may be the logs for that host
In NIDS a copy of the network traffic is taken and then copied to a storage area for analysis
How does a user interact with a firewall ?
User interface
What are the two methods the IDS/IPS uses to capture traffic ?
Inline captures, analyses and blocks the traffic as it flows through the device on which it is installed (usually a router). The downside is that if it suffers a malfunction then there is no checking
Passive takes a copy. However its retrospective so that it will allow the traffic to pass before making a judgement.
What are the inbound and outbound methods of the IPS ?
Inband checks the info and acts on it as it flows through the device. However there are performance implications so it should only be used for high value assets.
Outbound uses the passive approach so suffers from being reactive.
What are the types of IDS/IPS ?
Signature, Heuristic, Anomaly, Behavioural
What is a signature based IDS/IPS ?
This is essentially a matching process between the signature and the activity. Its very dependent on having the latest version of the signatures in the databases.
Because the database is constantly expanding there are potential performance implications that have to be accounted for.
This is also known as blacklisting.
What is an anomaly based IDS/IPS ?
Anomaly base systems learn the system and derive what it believes as normal and anything deviating from that are considered anomalies.
What is a behaviour based IDS/IPS ?
In this approach a baseline of good behaviours is defined which represents normal on the network. Anything that doesnt fall into line with this behaviour is blocked.
However changes in business process etc can lead to a initial high level of false positives.
What is a heuristic based IPS/IDS ?
Heuristic uses algorithms to predict what is malicious. They need to have these algorithms tweaked and can describe something as being not good but not malicious and let it pass.
What is a bridge ?
Bridge - Connect different segments together - Segmentation increases security by creating boundaries. Operates at level 2 of OSI model
What are SSL/TSL Accelerators ?
SSL/TSL Accelerators - Acts as a throughput between web servers and internet done on large scale operations using ssl to prevent bottlenecks
What are SSL Decryptors ?
SSL Decryptors - Allows authorised personnell to decrypt ssl traffic for inspection
What is a HSM ?
store and generator of encryption keys more efficient than general purpose keys