Transcript powerpoint

Protecting
Network Quality of Service
Against
Denial of Service Attacks
Douglas S. Reeves  S. Felix Wu
NC State / UC Davis / MCNC
DARPA FTN PI Meeting
August 2, 2001
NC State / UC Davis / MCNC
Timetable and Participants
• Start date = August 1999
• Duration = 36 months (+extension)
• Point of contact = Dr. Kevin Kwiat, AFRL,
[email protected], (315) 330-1692
Douglas Reeves, Peter Wurman
N.C. State University
{reeves,wurman}@csc.ncsu.edu
(919) 515-2044
S. Felix Wu
U.C. Davis
[email protected]
(530) 754-7070
Dan Stephenson,Xiaoyong Wu
MCNC
{stevenso,xwu}@mcnc.org
• No clearances
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Scope of the Project
Category
Control Flow
Protect
Intserv
Detect
Attacks
NC State / UC Davis / MCNC
Data Flow
Protect
Prevention from
Misuse
Detect Attacks
•RSVP
authenticat
ion
•Pricing
•Trust-based
allocation
•Reliable multicast
1.
DiffServ
•Reliable
Queue
Management
multicast
•Packet
dropping
analysis
2.
Security
Policy
Application
level
Traceback
Intrusion •Pricing
detection
IPSec Policy
generation,
correctness
•Watermar
king,
Traffic
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correlation
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NC State / UC Davis / MCNC
Results
• Accomplished
– Approximately 15 published papers to date
– 5 students graduated, 7 more in progress
– Software: packet dropping attack analysis,
RSVP authentication, RSVP pricing, trustbased allocation (and more to come)
– Patent and standards submissions
– Collaborations with Nortel
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NC State / UC Davis / MCNC
Disappointments (Failures)
• Failure of QoS to be deployed on a widespread
basis in the Internet
– lack of security / fault tolerance a major reason?
• Pricing
– requirements for adoption
• TCP Packet Dropping attacks
– limitations of neural nets
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NC State / UC Davis / MCNC
1. DiffServ Intrusion Detection
• Work by Xiaoyong Wu of MCNC
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DiffServ Components
H
C
E
C
C
C
H
•Vulnerabilities
E
H
H
E
H
C
E
H
-Packet dropping
-Packet remarking
-Packet delaying
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NC State / UC Davis / MCNC
Intrusion Detection Architecture
• Network monitoring
– DiffServ aggregated flow
monitor
– Micro-flow traffic monitor
• Anomaly (statistical
analysis) detection
• Rule based detection
• Detection and analysis
result correlation
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Local & Remote
Correlation
Stat
Rule
DSMon TrafMon
Linux Kernel
DiffServ
Implementation
LibPCAP
Fast Packet
Capturing
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NC State / UC Davis / MCNC
Network Monitors
• Communicate with Statistical Analysis and Rulebased Detection Modules
• Monitor Both Aggregated Flows and Microflows
• DiffServ aggregated flow monitor
– Periodically extract statistical values from Linux
kernel using Traffic Controller Library (libtc)
– Bytes and packets delivered
– Over-limit and dropped packets
• Micro-flow traffic monitor
– Micro-flow is defined by a traffic filter
– Uses Fast Packet Capturing (libpcap)
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NC State / UC Davis / MCNC
NIDES/JiNao Statistical Analysis
(Anomaly-based detection)
• Goodness of Fit Test
– H0: The data follows a "given" distribution
– H1: The data does not follow the specified distribution
• Obtain the Chi-Squared Value
– O = Observed value
– E = Expected value
– c2 = S (((O-E)2)/E)
• Notes
– The range of c2 is from 0 to infinity
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NC State / UC Davis / MCNC
Similarity “Score”
• Counting Measures
– Byte count and packet count
• Score Value - "Normalized" Q Value
– S = F-1(1-(TP/2))
– TP = Pm + Pm+1 + ... + Pmax
 F is the cumulative distribution function of a N(0,1)
variable
– Pm is the relative frequency with which c2 belongs to the mth
interval
– M and max are manually selected at present
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NC State / UC Davis / MCNC
Long Term Q Distribution Examples
• Background Traffic
(Poisson)
– 4Mbps
– Byte counts
• Audio Traffic
(Periodic)
– 64Kbps
– Byte counts
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NC State / UC Davis / MCNC
Rule Based Detection
• Meant to Detect Known Attacks and
Vulnerabilities
• Rules from RFC's and Real Deployments
– Expedited Forwarding
• No-Dropping Rule of inlimit traffic
• No-Overlimit Rule, within diffserv network
– Static Traffic Markings (DSCP's)
• Mark Mapping Rule for a microflow
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NC State / UC Davis / MCNC
Attack Implementation
• Linux Kernel Module
– Runs in kernel space
– Uses proc file system to configure
• Emulated Scenarios
– Planned: tunable packet delay distributions
– congestion and background loss – aggregated flow
– bandwidth limitation -- microflow
– Planned: packet reordering / duplication
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Traffic Generation Tools
• tcpTalk
– Audio Traffic
– TCP
• MGEN
– Background Traffic and Attack Traffic
– UDP
– CBR or Poisson
• Thttp (future)
–
–
–
–
Background Traffic
TCP (HTTP, FTP, SMTP, NNTP, etc.)
Emulate the traffic at the Internet core
Generate the packets based on the pre-calculated distributions
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NC State / UC Davis / MCNC
Detection Scenario and Performance
•
•
R1, R2 are 2 DiffServ routers with IDS
running
– R1 and R2 collect long term behaviors for
BE traffics and EF traffics
– R1 is compromised and starts to mark
one BE flow as EF
– Rule detection on R2 notices change of
marking for BE flow
– Accumulated increased EF traffics deviate
from the long term EF behavior
– Stat analysis on R2 notices the deviation
Performance
– With 1% false alarm rate we can get
100% detection rate
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BE
EF
R1
R2
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Detection Results
STAT
FLOODING
DROPPING
REMARKING
--STEALING
REMARKING
--SWITCHING
Yes
Yes
Yes
D/S
No
Yes
Yes
RULENo
Based
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Collaboration and Future Work
• Collaboration with Avaya Systems
– Network evaluation for Voice over IP solutions
– Interested in the impact of intrusions on voice traffic
– Interested in monitoring mechanisms
• Local and Remote Correlation
– Bayesian belief networks
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2. IPSec Policy Generation and
Correctness
• “Policy conflicts” for IPSec/VPN:
– what will possibly go wrong?
• Requirement versus Policy
– what are their relationship?
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NC State / UC Davis / MCNC
IPSec Policy:
Implementation Policy
• Policy:
– if <condition> then <action>
• IPSec policy:
– Condition: src,dst,src-port,dst-port, protocol, …
– Action:
Deny | Allow | ipsec (entry, exit, mode, sec-prot, alg)
• Example:
– Condition: src=A, dst=B, port=*, prot=TCP
– Action:
ipsec (Rb, Rd, tun, ESP, 3DES)
Rb,Rd, ESP A, B
A
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Rb
A, B
Rc
Rd
B
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Example Conflict #1:
Privacy and Content Examination
X
A
Y
SG-1
SG-2
B
(1.[srcIP=A dstIP=B prot=TCP srcPort=ANY dstPort=ANY] 
IPSec Prot=ESP Mode=Transport
Algorithm=3DES
from=A to=B)
(2.[srcIP=* dstIP=* prot=ESP srcPort=ANY dstPort=ANY]  deny )
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NC State / UC Davis / MCNC
Example Conflict #2:
Selector Confusion
X
A
Y
SG-1
SG-2
B
(1.[srcIP=A dstIP=B prot=ANY srcPort=ANY dstPort=ANY] 
IPSec Prot=AH Mode=Tunnel
Algorithm=HMAC-SHA
from=A to=SG-2)
(2.[srcIP=A dstIP=B prot=ANY srcPort=ANY dstPort=ANY]  allow)
(3.[srcIP=* dstIP=* prot=ANY srcPort=ANY dstPort=ANY]  deny )
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NC State / UC Davis / MCNC
Example Conflict #3:
Tunnel Overlapping
SG-1.1, SG-2
A
A, B
A, B
SG-2
B
SG-1.1
SG-1
SG-1,SG-2.1
SG-1.1, SG-2
SG-2.1
A, B
SG-1.1, SG-2
A, B
(1.[srcIP=A dstIP=B prot=ANY srcPort=ANY dstPort=ANY] 
IPSec Prot=ESP Mode=Tunnel
Algorithm=3DES
from=SG-1.1 to=SG-2 )
(2.[srcIP=* dstIP=* prot=ANY srcPort=ANY dstPort=ANY] 
IPSec Prot=ESP Mode=Tunnel
Algorithm=Blowfish
from=SG-1
to=SG-2.1)
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NC State / UC Davis / MCNC
Policy Conflict
IPSec/VPN Policy
• A set of (implementation) policies does not quite
work well together such that the packets
(information bits) are either dropped or
revealed/sent unsafely.
• Requirement(s): Intention(s) behind the
implementation-level policies:
• e.g., I want to maintain the privacy of certain flows:
– IPSec ESP Tunnels.
• Conflicts:
• a set of policies together does not support the requirements
• requirements conflict among themselves.
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NC State / UC Davis / MCNC
Policy versus Requirement
• Policy: (implementation, low-level)
• How should a network entity or a policy domain handle a
particular flow of packets functionally?
• Currently, the processing is based on the selector (i.e.,
the packet header information).
• Requirement: (intention, high-level)
• How should a particular set/flow of packets (information
bits) be protected and handled from A to B?
• Even if the packet header changes, the information bits
in the payload should still be protected in the same way.
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Policy versus Requirement
NC State / UC Davis / MCNC
a set of policy
a requirement
or
a set of policy
a set of policy
a requirement
a set of policy
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NC State / UC Davis / MCNC
Policy Analysis
a requirement
a requirement
a set of policy
a set of policy
a set of policy
????
a requirement
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NC State / UC Davis / MCNC
IPSec Security Requirements (1)
• Access Control Requirement (ACR)
– Restrict access only to trusted traffic
• E.g. Deny all telnet traffic
• Security Coverage Requirement (SCR)
– Apply security functions to prevent traffic from
being compromised during transmission across
certain area. +who can be trusted?
trusted
H1
Rb
Rd
H2
Encryption or Authentication
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NC State / UC Davis / MCNC
IPSec Security Requirement (2)
• Content Access Requirement (CAR)
– Specify the needs to access content of certain traffic
CMR: modify
CER : examine
I will examine the content for intrusion detection
• Security Association Requirement (SAR)
– Specify trust/distrust relationship in SA setup
X
Can not set up SA
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NC State / UC Davis / MCNC
Security Requirement Satisfaction (1)
• Access Control Requirement - deny or allow
• Security Coverage Requirement
– All the links and nodes in the area will need to be covered
by specified security
No!
H1
Rb
Rc
Rd
H2
Rd
H2
Encryption
Yes!
H1
Rb
Rc
Encryption
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NC State / UC Davis / MCNC
Security Requirement Satisfaction (2)
• Content Access Requirement
– Certain node needs to access the content, Rb? Rc?
Rb: No!
Rc: Yes!
H1
Rb
Rc
Rd
H2
• Security Association Requirement
– Some nodes are not allowed to set up SA
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IPSec Requirement Spec.
• Formal specification:
• ACR-SCR-CAR-SAR
• Conflict Detection in Requirements:
• Requirement Satisfiability Problem (RSP): given a set of
requirements, an algorithm to check whether at all possible to
find a set of policies to satisfy all the requirements.
• Completeness Proof
• Policy Determination:
• Transformation: if possible, an algorithm to find the “optimal”
set of policies.
• Correctness and Efficiency
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Example (per flow):
1
2
SCR#1:
Coverage:
SCR#2:
SCR#3:
Content:
CAR#1:
SAR#1:
SA relation: SAR#2:
SAR#3:
August 2, 2001 -- FTN PI Meeting
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4
5
ENC 2-4 trusted 3
AUTH 1-4 trusted 3
ENC 3-5 trusted 4
(ENC, AUTH)
by 4
not-ENC
2-5
not-ENC
1-5
not-AUTH
1-4
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NC State / UC Davis / MCNC
Solution:
ENC
ENC
AUTH
1
AUTH
2
3
SCR#1:
Coverage:
SCR#2:
SCR#3:
Content:
CAR#1:
SAR#1:
SA relation: SAR#2:
SAR#3:
August 2, 2001 -- FTN PI Meeting
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5
ENC 2-4 trusted 3
AUTH 1-4 trusted 3
ENC 3-5 trusted 4
(ENC, AUTH)
by 4
not-ENC
2-5
not-ENC
1-5
not-AUTH
1-4
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Policy Generation CPU Time
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Number of Policy Rules Generated
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Results
• Collaboration with Nortel Networks
• For more information:
– Policy’2001: requirement specification language
– DSOM’2001: automatic policy generation algorithms.
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