PSC CyberSecurity 3 Networks v1

Cri$cal Infrastructure Security: The Emerging Smart Grid

Cyber Security Lecture 4:

Network Vulnerabili$es & Mi$ga$ons Carl Hauser & Adam Hahn

Overview

•  Network AHacks – DoS – Spoofing

•  Mi$ga$ons – Cryptographic Protocols – Firewalls –  Intrusion Detec$on

Denial of Server (DoS) AHacks •  Defini$on

–  “DoS is an ac$on that prevents or impairs the authorized use of network systems, or applica$ons by exhaus$ng resources such as central processing unit (CPU), memory, bandwidth, and disk space”

•  Techniques

–  Malformed packet •  malformed packet that triggers some soWware vulnerability/weakness causing a system crash

–  Flooding •  overwhelming system resources (e.g., network bandwidth, CPU speed)

–  Protocol-‐based •  Manipulate protocol state (e.g., TCP Reset)

•  Other DoS Types

–  DDoS – Distributed DoS –  Reflec$on/Amplifica$on –  Non-‐malicious – slashdoHed, flash crowd

Flooding •  Goal: Overload the capacity of the network/system

–  Network – consume resources (e.g., bandwidth) –  System – exhaust system’s ability to process data

•  Types –  ICMP Flood

•  ICMP Echo Request” messages -‐ oWen filtered •  ICMP Des$na$on Unreachable -‐ not as commonly filtered

–  UDP Flood •  send large UDP packets to some system (e.g., DNS) •  UDP connec$onless so no TCP handshake overhead

–  HTTP Flood •  sending legi$mate HTTP GET/POST messages to web server

Flooding -‐ Con$nued •  TCP Syn Flood –

–  How •  AHacker sends large number of TCP Syn packets to server •  Server creates half-‐open connec$on and sends Syn-‐Ack •  Client doesn’t send Ack to open connec$on

–  Result •  AHack exhausts finite list of half-‐open connec$ons allowed by opera$ng system

–  Defense •  AWer server send Syn-‐Ack, removes entry from Syn queue •  Stores “Syn cookies” which encodes IP addresses/ports, sequence numbers

•  Prevents exhaus$on of Syn queue –  Old aHack method, but may s$ll be a vulnerability on legacy control system devices

Malformed Packet

•  Causes soWware or opera$ng system to crash – Usually result of soWware vulnerability/error

•  Example –  Ping of Death –

•  ICMP “ping” packet > 216 bytes violates protocols •  Caused buffer overflow/crashing of older Windows/Unix systems

–  Teardrop •  Targets incorrect reassembly of fragmented IP packets •  Overlapping fragments caused opera$ng system to crash

Reflec$on •  Reflec$on

–  How •  AHack system spoofs IP address of intermediate system •  Intermediate system responds to target system •  Vic$m thinks aHack originates from intermediate system, not aHacker

–  Why •  AHack less likely to be iden$fied •  AHack bandwidth can be amplified

–  Example protocols: •  TCP handshake •  UDP (DNS, NTP, SNMP)

–  aHacker doesn’t have to set up sessions!

Reflec$on Example: TCP

Normal TCP Handshake

•  Normal TCP Handshake

•  TCP Syn spoofing –  Spoofed Syn causes server to con$nually send

Syn-‐Acks to target system

DDoS •  Distributed DoS

–  U$lize large number of aHacking systems –  Improves amount traffic sent by aHack –  More difficult to prevent

•  Can’t filter single system •  Difficult to differen$ate aHack from normal traffic

•  Control –  Centralized

•  Single aHack has control over large number of systems (e.g., botnet) •  Example: hHp://blog.cloudflare.com/65gbps-‐ddos-‐no-‐problem/

–  Distributed •  AHacks launched by individual par$es (e.g., Anonymous) •  OWen u$lize botnets to perform the DDOS •  Example:

–  hHp://bits.blogs.ny$mes.com/2012/11/15/anonymous-‐aHacks-‐israeli-‐web-‐sites/

More DDoS Examples

•  65 GB DoS aHack – hHp://blog.cloudflare.com/65gbps-‐ddos-‐no-‐problem/

– 65,000 systems with 1Mbps link (upstream)

•  Amplifica$on – Assuming 60 byte request, 512 byte response – ~7617 systems required for the DoS aHack

Overview



IP Spoofing

•  IP developed without authen$ca$on capabili$es (1970s) –  Source address can be spoofed so receiver thinks sender was someone else

–  S$ll seen frequently (usually with DoS aHacks) •  Security Mechanisms:

–  Routers – may filter packets with incorrect source IP addresses

–  IPsec – provide authen$ca$on of IP packets –  IPv6 – default support for IPsec

ARP Spoofing

•  Recall – ARP – Address Resolu$on Protocol –  Know the IP address, but not the MAC (link address) of a system

•  Problem – ARP messages aren’t authen$cated – AHack can create malicious ARP Response claiming to be the systems with the requested IP

– Generally a race between aHacker and actual target •  Security Mechanisms:

–  Sta$c arp tables on hosts/network switches

ARP Spoofing

Attacker

Normal ARP ARP Req: who is 1.2.3.4

ARP Resp: 1.2.3.4 is

00:11:22:33:44:55

Dst Mac= 00:11:22:33:44:55

ARP Req: who is 1.2.3.4

ARP Resp: 1.2.3.4 is

00:11:22:33:44:55:66

ARP Resp: 1.2.3.4 is 11:11:11:11:11:11:11

Dst Mac= 11:11:11:11:11:11:11

Source

Spoofed ARP

ARP Req: who is 1.2.3.4

Destination IP: 1.2.3.4 MAC: 00:11:22:33:44:55

Destination IP: 1.2.3.4 MAC: 00:11:22:33:44:55

Other Spoofing •  TCP – stateful connec$on

–  Has sequence & acknowledgement numbers –  Packets with incorrect sequence numbers will be rejected

•  Inside current “Receive Window” –  Sequence number (232 bit number) –  Randomized Ini$al Sequence Numbers (ISNs) to prevent a users from guess

the number •  Not helpful if the aHacker can view your TCP session and obtain current sequence

numbers

•  BGP – Boarder Gateway Protocol –  Malicious system can adver$se false rou$ng paths to hijack traffic –  Examples

•  hHp://www.cnet.com/news/how-‐pakistan-‐knocked-‐youtube-‐offline-‐and-‐how-‐to-‐make-‐sure-‐it-‐never-‐happens-‐again

•  hHp://www.bgpmon.net/chinese-‐isp-‐hijacked-‐10-‐of-‐the-‐internet/ •  hHp://www.bgpmon.net/turkey-‐hijacking-‐ip-‐addresses-‐for-‐popular-‐global-‐dns-‐

providers/ •  hHp://www.bgpmon.net/the-‐canadian-‐bitcoin-‐hijack/

DNS Spoofing •  Originally DNS didn’t have any authen$ca$on

–  AHackers could spoof DNS response to get a user to visit a different system –  If MITM aHack

•  Simply manipulate DNS response –  If Spoofing only (i.e. no ability to see current traffic)

•  DNS request – unique 16 bit “Query ID” •  If response Query ID != request Query ID -‐> disregard response •  Before ~2008 Query ID was sequen$al

–  AHacker could guess future query IDs and inject spoofed DNS responses

•  Examples –  China manipulated DNS records for sites

•  hHp://www.computerworld.com/ar$cle/2516831/security0/china-‐s-‐great-‐firewall-‐spreads-‐overseas.html

–  Turkey manipulated DNS to block TwiHer •  hHp://www.theguardian.com/world/2014/mar/21/turkey-‐blocks-‐twiHer-‐prime-‐minister

•  Security Mechanisms –  Randomize DNS Query ID –  Spoofed DNS response must also have correct Dst. Port –  DNSSEC

DNS – Spoofing

Internet

RandomSite Network

Local Network

Root Name Server

Local Name Server

RandomSite.com Name Server

1 2 3

6

8 .Com Name Server

4 5

www.RandomSite.com

9

DNS HTTP

10

7

aHacker.com

Overview


•  Mi$ga$ons –  Cryptographic Protocols – Firewalls –  Intrusion Detec$on

Security Protocols

Network (Ethernet)

Internet (IP)

Transport (TCP/UDP)

Applica$on (HTTP,DNS)

TCP/IP Stack Security Protocols

TLS

Internet (IPSEC)

HTTPS/ DNSSEC

Network (802.1x)

Transport (TCP/UDP)

Unsecure Secure

•  Necessary to communicate securely across untrusted network –  Provide integrity, confiden$ality, authen$city of communica$ons

–  Based on previously discussed cryptographic mechanisms

Transport Layer Security (TLS)

TLS

•  Previous Secure Sockets Layer (SSL) •  Originally designed to support secure HTTP (HTTPS) – Runs over TCP – Datagram TLS – TLS equivalent for UDP – Currently used to secure many other protocols

•  Provides: – Authen$ca$on/Integrity – uses MACs – Confiden$ality – encryp$on of messages

TLS/SSL Versions •  Older

–  SSL 1.0-‐2.0 – well known security vulnerabili$es –  SSL 3.0 – weak key genera$on

•  Government Approved (based on NIST SP 800-‐52 rev 1) –  TLS 1.0 – not significantly different than SSLv3

•  Only when dealing with business/public (not govt only comm.)

•  Browser Exploit Against SSL/TLS (BEAST) vulnerability –  TLS 1.1 – fixes some issues with CBC mode, other fixes –  TLS 1.2 – specify SHA-‐2 (256,512 bit) hash func$ons

TLS Protocol Stack

Type: Handshake

•  Stateful connec$on •  Handshake used to communicate/agree on various parameters – TLS/SSL versions – Ciphers – Cer$ficates – Pre-‐master secret – Master secret – Session ID

TLS Handshake

Proposes 1) version, 2) ciphers, 3) session ID, 4) random number

Specifies: 1) version, 2) cipher, 3) random number

Server cer$ficate Public key parameters

Change cipher suite (encrypted in future)

Change cipher suite (encrypted in future)

Client cer$ficate (op$onal)

Premaster secret

TLS Ciphers

•  Cipher contains set of crypto algorithms necessary to perform following func$ons: – Key exchange algorithm

•  E.g. RSA, Diffie Hellman, ECDH

– Bulk encryp$on algorithm •  Stream(RC4, etc.), Block(3DES, DES, AES, etc.)

– Data Integrity/Auth. •  MAC algorithms, HMAC with (MD5, SHA1, SHA256)

IPsec •  Commonly used to build “secure” VPNs

–  Host to host, network to network, host to network

•  Encryp$on and authen$ca$on at the network layer

•  Func$ons –  Security Associa$ons

•  algorithms and parameters used in encryp$on –  Authen$ca$on Header (AH) – Deprecated…

•  connec$onless authen$ca$on and integrity –  Encapsulated Security Payload (ESP)

•  Provides confiden$ality, authen$ca$on, integrity

Benefits

•  Provide confiden$ality, integrity, authen$ca$on of all IP packets (routable traffic) – Transparent to users

•  Can move crypto processing oWen moved to network routers/devices rather than the system

Security Associa$ons

•  One way rela$onship between sender and receiver about security protocol parameters –  Algorithms and keys used to protect the communica$on –  Need two SAs for two way communica$on

•  Includes –  Security Parameter Index (SPI)

•  iden$fier for the SA –  IP des$na$on address

•  des$na$on endpoint of the SA –  Crypto algorithms/keys

•  SA establishment relies on ISAKMP protocol

ESP Modes -‐ Examples

Trusted Network A Trusted Network B

IPsec (Tunnel)

External Hosts Unsecure Connec$on External Hosts

IPsec (Transport)

TLS vs IPsec

•  Connec$on Establishment –  IPSec – pre-‐established “Security Associa$ons” to agree on ciphers, etc.

•  Addi$onal overhead –  TLS – u$lizes handshake to nego$ate between client/server

•  Vulnerable to MitM “downgrade” aHacks

•  Trust Establishment –  IPSec – pre-‐established during SA

–  TLS – based on •  trusted cer$ficate authority

•  pre-‐shared cer$ficates

IEC 62351

•  Data and communica$ons security standard for power systems

•  Provides standard for –  IEC 62351-‐9 – Key management

•  X509 cer$ficates for devices •  Group Domain of Interpreta$on (GDOI)

–  Symmetric key management –  Based on trusted key server

–  TLS for message encryp$on –  RSA based digital signatures for message authen$ca$on

hHp://iectc57.ucaiug.org/wg15public/Public%20Documents/White%20Paper%20on%20Security%20Standards%20in%20IEC%20TC57.pdf

Overview

•  Network AHacks – DoS – Spoofing – Tampering


Firewalls

•  Why? –  Separate more cri$cal/less cri$cal networks

•  Restrict Internet traffic to systems –  Enforce desired traffic flows/security policies

•  How? Single system that all traffic must pass through –  Enforces rules on all traffic

•  Ingress – data coming in to network •  Egress -‐ data leaving network

Firewall Types

•  Firewall Types – Packet Filtering

•  Stateful inspec$on – Applica$on-‐Layer proxy

•  Operate a different layers in the TCP/IP stack

TCP

UDP

HTTP

DNP

DNS

TCP/IP Stack

IP

ICMP

Network/Link

Internet Transport

Applica$

on

Packet Filtering •  Generally operate at the Network/Internet/Transport

layers •  Configura$on includes

–  “Default Policy” for traffic that doesn’t match rule •  Discard/Drop – prohibit the packet •  Forward/Accept – allow the packet

–  “Rules” to match packets •  Packet matching informa$on

–  Source/Des$na$on IP –  Source/Des$na$on Port –  Protocol (e.g., TCP/UDP)

•  Ac$on –  Accept/Deny

–  Called “Stateful Inspec$on” if aware of TCP connec$ons

TCP

UDP

HTTP

DNP

DNS

TCP/IP Stack

IP

ICMP

Network/Link

Internet Transport

Applica$

on

Packet Filtering Example Rules •  Only allow control traffic to DNP slave (IP:1.2.3.4, TCP 20000)

–  External – IP range of external systems –  Remember: source ports for TCP connec$ons usually use ephemeral

ports range (high number)

Rule DirecLon Src Addr Src Port Dst Addr Dst Port Prot Conn State AcLon

1 In External -‐-‐-‐-‐ 1.2.3.4 20000 TCP New, Established Permit

2 Out 1.2.3.4 20000 External -‐-‐-‐-‐ TCP Established Permit

3 Both Any Any Any Any Any New, Established Deny

Applica$on Firewall

TCP

UDP

HTTP

DNP

DNS

TCP/IP Stack

IP

ICMP

Network/Link

Internet Transport

Applica$

on

•  Designed specifically for applica$on layer protocol

•  Example: – Web Applica$on firewalls – SCADA applica$on filtering

•  DNP3 -‐ Objects •  IEC 61850 – Goose messages

Overview

•  Network AHacks – DoS – Spoofing – Tampering


Intrusion Detec$on

•  Intrusion Detec$on System (IDS) –  Iden$fies aHacker aHempts to gain unauthorized access to networks or systems

•  Components –  Sensors – collect data (e.g., network packets, log files, system calls) –  Analyzer – receives input from sensors and analyzes it for

IDS Categories •  Sensor Types

–  Host-‐based (HIDS) – sensors collect data from hosts for malicious processes, network stack ac$vity, modified files, etc.

–  Network-‐based (NIDS) – sensors collect data from network –  Hybrid – combine informa$on from both network and hosts

•  Analysis Types –  Signature-‐based – use set of know aHack paHerns that are compared with current sensor data (e.g., Snort)

–  Anomaly based – compare current data to collec$on of past data, assumes devia$on from past paHerns (or anomalies) are aHacks

–  Specifica$on-‐based – create “specifica$on” of known, correct system opera$on.

Anomaly-‐based Detec$on •  Overview:

–  Develop model of normal behavior and compare incoming events

•  Approaches –  Sta$s$cal model or machine learning approach to categorizing traffic

as normal or malicious

•  Strength –  Can detect new/unknown aHacks!!!

•  Weakness –  Many benign anomalies (e.g., network reconfigura$on, system

upgrades, new programs) –  Excessive False Posi$ves (Base Rate Fallacy) –  AHacks that are not anomalies?

Basic Detec$on Theory

•  IDS requires small –  False posi$ves

•  wastes money/resources inves$ga$ng non-‐aHack –  False nega$ves

•  missed aHack results in viola$on of security policy –  Base Rate Fallacy

•  Small number of intrusions, vs large number of non-‐malicious traffic •  Accurate IDS will s$ll raise large number of false posi$ves

•  IDS performance can be represented by a receiver opera$ng characteris$cs (ROC) curve

ANack Present

ANack IdenLfied

False Posi$ve

False Nega$ve

True Nega$ve

True Posi$ve

Yes No

Yes

No

False Posi$ve

True

Posi$ve

0.0 1.0

1.0

0.0

Signature-‐based Detec$on •  Overview:

–  maintain collec$on of known paHerns of malicious data, compare incoming network traffic to paHerns

•  Strength –  Low False Posi$ve rate (if rules created correctly)

•  Weakness –  Can’t detect novel (0-‐day) aHacks, detec$on only works when it has previous

•  Example: –  Snort IDS

Snort IDS •  Open-‐ source Signature based IDS

•  Modes –  Passive – only detect aHacks –  Inline – can block packets

•  Intrusion preven$on

•  Architecture –  Decoder

•  decode protocol layers, structure packet for analysis –  Detec$on Engine

•  analyzes packet vs set of rules –  Logger/Alerter

•  perform necessary response

Snort Rules •  Ac$on: what do to when you iden$fy a packet

–  Examples: alert, log, pass, drop, reject, ac$vate, etc •  Protocol, Port, IP Address, Direc$on

–  Example: “tcp any any -‐> 192.168.1.0/24 111” •  Op$ons

–  General – informa$on without impact on detec$on •  Examples: msg, ref(URL), classtype, priority

–  Payload – specify packet payload informa$on •  Example: content, offset, pcre, hHp_header,

–  Non-‐payload – specify non-‐payload data •  Example: Hl, seq, ack,

–  Post-‐detec$on – specify rules for aWer rule operates •  Example: resp, react, session

•  More info here (hHp://manual.snort.org/node27.html)

PSC CyberSecurity 3 Networks v1

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