A general overview of botnets

1. BOTNET COMMUNICATION
PATTERNS
CS-B
Neelesh Kisku
MNNIT Allbd

2. Overviews
 Botnet topologies
 Command and Control centers (C&C) protocols
 Botnet objectives
 Botnet establishment and operations
 Detection methods and evolution
 Taxonomy generalized communication patterns
 UML sequence diagrams
 Data exchange options
 Encryption and hiding techniques
 Building protocol and topology independent
networks-based detectors

3. Introduction
 Networked computers enable distributed
computing and sharing of resources. Distributing
tasks over multiple machines allow the execution
of tasks.
 The are divided into Bots (doing task/sub-task)and
Master(C&C)
 Internet consist vast amount of unused processing power
and network bandwidth
 This is achieved by malware coordinating a botnet using
compromised machine for computation

4. Malicious Botnet
 These offer various task & service like theft
(identity theft), service disruption (network
architecture)
 Thus various taxonomies and recommendations
categorizing different aspects of botnet and
ways of detections seen
 These are protected from takeover from 3 rd
parties thus many ways arise to mitigate
bringing down of botnet via single point of failure
 Botmasters the controllers stay stealthy to avoid
potential prosecution by using little traffic and
less possible direct connection

5. Botnet Detector
 We can target communication pattern as network
is paramount for operation (network based)
 Or extract communication excerpts and compare
result with traffic (signature based)
 Classify network traffic normal/anomalous
(behaviour based)
 Countermeasures padding (add sequence of
data), protocol encryption
 As no inspection of payload is needed
generalized properties of obfuscated network
traffic can be theoretically used to detect
unknown bots

6. Machine Learning
 Analyzing packet meta data to predict
expected output from given inputs (training)
not necessarily correlating data
 Filtering step introduced for automated feature
selection (scoping)
 Black list for false positive benign nodes as
C&C
 Thus high accuracy seen during training for
related botnet detected goal of unknown
botnet not realised

7. Related work (I)
 Analysis of attack classes , propagation mechanisms
from OS to applications and social engineering (spam)
 Bot life cycle consisting infection , rallying ,
commands/report and abandon
 Changing botnet techniques and environment , single
bot and HTTP based botnet detection
 Comparing stationary and mobile botnets
 Without need of training for signatures based on basic
infection consisting inbound scan , implying infection ,
egg(executable bin) download , outbound scan for C&C
communication

8. Related Work (II)
 Detector using IDS to match event to rules from
infection dialogue
 Infection model split as per network activity and
cross co-relating with common botmaster
 Detector based on bayesian network
 As the events evolve and parts responsible change
 Communication perspective (in depth look)
 C&C description
 Sequence messages (botnet communication
pattern)
 Framework for building detectors (UML sequence
diagrams)

9. Botnet Topology
 Bot functionality and C&C can be same or
distributed across

11. Centralized
 Centralized dedicated server easy to set up , low
latency high scalability no special requirements
(protocol)
 Low robustness C&C being single point of failure
 Address needs to be hardcoded thus obfuscated
 Mitigates using DGA algo can create fast-flux
network
 Query local system or internet for DGA to stop
takeover
 URL based spam detection defeated

12. Overhead

13. P2P
 Every bot potential server
 Low communication latency , high robustness ,
less scalability
 OS limits bot size max no. of bots on concurrent
TCP connection
 Increased visibility low stealth
 High no. of coordinating messages thus not fully
mesh
 Does maintain cache server (peer list) or is
hardcoded
 Neoteric protocol for fallback channel if comms

15. P2P

16. Botnet Protocols (I)
 Protocols are tailored to stealthiness achieved
by mimicking legitimate traffic
 They depend on development , network
restrictions
 Generally used are existing and neoteric
protocol
 Types are
1) IRC : Text based may be password protected
2) HTTP : Request response based high
latency, major problem loops flooding bot with

17. Botnet Protocols (II)
3) SMB : Server Message Block (eg. Shared
printers) there we request list of available file
shares/services pool , (IPC) named pipes call
specific functions
4) P2P Protocol : WASTE and KADEMLIA used to
store value hashes uses cache servers and used
for file sharing
5) Neoteric Protocol : UDP/TCP unreliable single
packets vs. reliable stream may require network
overhead and payload can be binary/text based

18. Communication Hiding &
Obfuscation
 Covert Channel : Using unused header bits eg.
Identifier field
of ICMP
 Encryption : Stream/Block based ;
Symmetric/Asymmetric cipher
 Multiple Protocols
 Compression : Replace repeating sequence
 Steganography : carrier files not meant for comms (eg.
Images)
 Proxying

19. Communication Patterns (I)
 Notation
 Sequence of exchange mssg. for task draws UML
diagram
 Mssg. are synchronous/asynchronous
 Contains request page and page contents (arrow) ,
additional combined fragment and operator kind
(box/bracket) , interaction use ie. parts without
constraint
 Divided into :
1)Coordinate 2)Scan 3)Data 4)Register
5)Store/Execute/Infect/Compute

20. Communication Pattern(II)
 Overview
 C&C traffic can be bot or server
 Action can be monitored stealth of
coordination required
 Communication can be push/pull
 Botnet communication diveded into
operationand propogation

21. Communication Pattern(III)
 Propogation
 This happens actively or passively
 Passive : 1)Click fraud
2)Drive by
 Active : 1)Existing vulnerability exploit
2)Coordination of scan OS and network
 Registration

22. Operation
 Data upload
 Data download
 Forward proxy
 Reverse Proxy
 Instructions

23. Conclusion
 Event generation engines can be used (IDS)
 Machine learning to reorganize message
exchange
 Identifying botnet communication
 Detection of encrypted protocol C&C patterns
 Detector capable of matching comms. pattern
from independent C&C protocol , topology ,
family

24. UML

25. Related Research

26. Master Table

27. Propogation

28. Upload

29. Download

30. Proxy

31. Botnet Instructions

32. Communication

33. Recent

34. Recent

35. Recent

36. References
 Symantec corporations knowledge base
 Kaspersky threat list
 R M Lee “Analysis of cyber attack on ukranian
power grid”
 W32.Stuxnet dossier
 APT advanced persistent Threats