Attack Vectors and Mitigations

Attack Vectors ?

Network Security 2T. A. Yang

• http://en.wikipedia.org/wiki/Vector_%28epidemiology%29:

- In epidemiology, a vector is any agent (person, animal or microorganism) that carries and transmits an infectious pathogen into another living organism.

• http://searchsecurity.techtarget.com/definition/attack-vector:

- In computing, a vector or attack vector is a path or means by which a hacker can gain access to a computer or network server in order to deliver a payload or malicious outcome.

- Attack vectors enable hackers to exploit system vulnerabilities, including the human element.

- Attack vectors include viruses, e-mail attachments, Web pages, pop-up windows, instant messages, chat rooms, and deception. All of these methods involve programming (or, in a few cases, hardware), except deception, in which a human operator is fooled into removing or weakening system defenses.

Vector vs Payload

• http://cybercoyote.org/security/vectors.shtml: – Don't confuse attack vectors with payloads. – payload : malicious code carried by attack vectors -- spyware,

Trojan-horses, dialers, destructive code and other malware. Some attacks deliver multiple payloads (warheads).

– For example, worms attack through the network connection to get in. That's just the first step. Worms usually carry an installer for malware, such as spyware or botware as their payload. The worm's work is done when the payload is installed and running on the computer.

T. A. Yang Network Security 3

Vulnerabilities• The million buck question:

Why not remove all vulnerabilities from the systems?

• At least two reasons:1.The computer and networking systems that we use today were designed and developed long before security was considered an important factor in computing. e.g., TCP/IP

2.New attacking schemes keep coming up.

Q: Is it possible to define a ‘perfectly secure’ system?

e.g., The castle was an almost perfect defense mechanism until big guns and airplanes emerged.

T. A. Yang Network Security 4

Types of Attacks• Reconnaissance

– Discovery and mapping of systems, services, or vulnerabilities

• Unauthorized access• Unauthorized modifications• Denial of service

– A service/resource is blocked, degraded, disabled, or corrupted and becomes unavailable to authorized users.

• Pattern of attack:– Mapping the potential victim’s system(s)– Gaining access to a user account– Escalating privilege– Exploiting the system (or using it as a jumping board)

T. A. Yang Network Security 5

Types of Attack Vectors• Viruses, Worms, Trojans, Password crackers• Buffer overflows• IP spoofing, ARP spoofing• TCP hijacking (a type of man-in-the-middle attacks)• Ping sweeps, Port scanners• Packet sniffers• Flooding, DoS/DDoS attacks• Rootkits and botnets (aka zombie army)

– The most prevailing threats as reported by the Kaspersky Labs and the Symantec.

– A master thesis (2011): A comparative analysis of rootkit detection techniques (available at http://sceweb.sce.uhcl.edu/yang/research/sampleTheses.htm)

T. A. Yang Network Security 6

Rootkits and botnets• http://searchsecurity.techtarget.com/definition/botnet:

– A zombie or bot is often created through an Internet port that has been left open and through which a small Trojan horse program can be left for future activation.

• http://en.wikipedia.org/wiki/Botnet:

– Computers are often recruited into a botnet by running malicious software. This may be achieved by luring users with a drive-by download, exploiting web browser vulnerabilities, or tricking the user into running a Trojan horse program, possibly in an email attachment. It will typically install modules which allow the computer to be commanded and controlled by the botnet's owner. The Trojan may delete itself, or may remain present to update and maintain the modules.

– The controller (aka master) of a botnet directs these compromised computers via standards-based network protocols such as IRC (Internet Relay Chat) and HTTP (Hypertext Transfer Protocol).

T. A. Yang Network Security 7

Mitigation Techniques against the Attacks

T. A. Yang Network Security 8

• What can and should be done to mitigate these attacks?– Viruses, Worms, Trojans, Password crackers– Buffer overflows– IP spoofing, ARP spoofing– TCP hijacking (a type of man-in-the-middle attacks)– Ping sweeps, Port scanners– Packet sniffers– Flooding, DoS/DDoS attacks– Rootkits and botnets (aka zombie army)

• Principles: defense in depth, controls at multiple layers

Mitigations at Layer 3• Deployed on layer-3 devices

– Firewalls– Routers– Layer-3 switches

• Example attacks at layer 3:– ICMP Flood (Smurf Attacks)– SYN Flood– DoS Attacks– IP Spoofing– Packet interception ?

T. A. Yang Network Security 9

L-3 Mitigation Techniques• Mechanisms in IOS

– Traffic characterization using ACL– IP source tracker– Antispoofing with ACL, uRPF, IP source guard– Packet classification and marking– Committed access rate (CAR)– Modular QoS CLI (MQC)– Traffic policing– Network-Based Application Recognition (NBAR)– TCP Intercept– Policy-Based Routing (PBR)– uRPF– NetFlow

T. A. Yang Network Security 10

Mitigations at Layer 2

• Deployed on layer-2 devices

• Bhaiji:– Layer 2 attacks are difficult to achieve from outside

the network.– The attacker needs to be inside the network to be

able to abuse layer 2.

• True? How about attacks against WLAN?

T. A. Yang Network Security 11

Example Layer-2 Attacks (and mitigations)

T. A. Yang Network Security 12

Attacks Mitigations ?

CAM Table Overflow (aka MAC attacks)

MAC Spoofing Attacks

ARP Spoofing Attacks

VTP Attacks

VLAN Hopping Attacks

Attacks against PVLAN

Attacks against Spanning Tree

DHCP Spoofing and Starvation Attacks

Attacks against 802.1x