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Transcript of Introduction to Botnets Instructors: Ali Shiravi, University of New Brunswick Natalia Stakhanova,...
Introduction to Botnets
Instructors:Ali Shiravi, University of New Brunswick
Natalia Stakhanova, University of South Alabama
Hanli Ren, University of New Brunswick
Part 1: Intro to BotnetsWhat are they?
In the news…
• July 29 2010 - Multi-Purpose Botnet Used in Major Check Counterfeiting Operation
• Aug 4 2010 - Zeus v2 Botnet that owned 100,000 UK PCs taken out
• Aug 12 2010 - dd_ssh Botnet attacks SSH servers
• Aug 12 2010 - Zeus ‘Mumba’ Botnet Seizes Confidential Database sized 60GB
• Aug 12 2010 - Zeus v3 botnet raid on UK bank accounts
3
IntroductionAttacker
(Botmaster )
Zombies
• Malware is currently the major source of attacks and fraudulent activities on the Internet.
• Malware is used to infect computers.
• Botnet is a network of zombies, i.e. compromised computers under control of an attacker.
• Bot is a program loaded on zombie computer that provides remote control mechanisms to an attacker.
4
Bot• Bot - a small program to remotely control a computer•
• Characterized by – Remote control & communication (C&C) channels to
command a victim• For ex., perform denial-of service attack, send spam
– The implemented remote commands• For ex., update bot binary to a new version
– The spreading mechanisms to propagate it further• For ex., port scanning, email
5
http://en.wikipedia.org/wiki/Botnet6
C&C channel
• Means of receiving and sending commands and information between the botmaster and the zombies.
• Typical protocols– IRC– HTTP– Overnet (Kademlia)
• Protocols imply (to an extend) a botnet’s communication topology.– The topology provides trades-off in terms of bandwidth,
affectivity, stealth, and so forth.
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Botnet Infection Stages - Centralized
8
Part 2 – How does a botnet operate?
10
Popular Botnets Propagation MethodsSpammed Messages
Social Networking Websites
Malicious Websites
Install MalwareBecome Bot
Removable Devices
Worm
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Shift in the way that malware is distributed
• Every 1.3 seconds a new web page is getting infected
• Every month almost 2 million web pages across 210,000 websites are infected with Malware
• Malware attacks have grown by 600% since 2008
12
Spammed Messages
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Spammed Messages
Storm Botnet
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Step 1: Click Link
Step 2:Link to malicious website
Step 3:Download & Run Malware
Propagation Steps
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Sample subjects and attachments
Sample subjects:
• A killer at 11, he's free at 21 and kill again!
• British Muslims Genocide
• Naked teens attack home director.
• 230 dead as storm batters Europe.
• Re: Your text
• Radical Muslim drinking enemies's blood.
• Saddam Hussein alive!
• Fidel Castro dead.
• FBI vs. Facebook
Sample attachments:
Postcard.exeecard.jpgFullVideo.exeFull Story.exeVideo.exeRead More.exeFullClip.exeGreetingPostcard.exeMoreHere.exeFlashPostcard.exeGreetingCard.exeClickHere.exeReadMore.exeFlashPostcard.exeFullNews.exeNflStatTracker.exeArcadeWorld.exeLeft-right-brain-test.gif
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Social Networking Websitese.g. Koobface
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Social Networking WebsitesKoobface Downloader
http://us.trendmicro.com
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Koobface Spam MessagesA typical KOOBFACE infection starts with a spam sent through:• Facebook• Twitter• MySpace• Other social networking sites
http://us.trendmicro.com
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Koobface Spam Messages
http://us.trendmicro.com
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Koobface Spam Messages
http://us.trendmicro.com
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Koobface Spam Messages
http://us.trendmicro.com
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Koobface Malware Download
Clicking the link will redirect the user to a website designed to mimic YouTube (but is actually named YuoTube), which asks the user to install an executable (.EXE) file to be able to watch the video.
http://us.trendmicro.com
23
Malicious Websitese.g. Gumblar Zeus
24
Malicious Websites
http://www.ipa.go.jp/security/english/virus/press/201001/E_PR201001.html
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Gumblar Compromised Website
The malicious script embedded in the website.
http://www.van-manen.info/weblog/2010/02/gumblar-virus-infecteert-microsoft-website/
26
Zeus Malware Download
27
Zeus Compromised host
Part 3 – How is a botnet organized?
Traditional botnetAttacker
Zombies
Commands & controls
Attack
Victim
Your home
computer
Infect
Botnet topology mainly refers to the organization of C&C channels between zombies and an attacker.
29
Topology• Based on C&C channels, there are two typical botnet topologies:
– Centralized– Decentralized (P2P)
• Traditional botnet metrics:– Resiliency
• A botnet ability to cope with a loss of members (zombies) or servers– Latency
• Reliability in message transmission– Enumeration
• An ability to accurately estimate a botnet size• Difficuly for security analysis
– Re-sale• A possibility to carve off sections of the botnet for lease or resale to other
operators.
30
Centralized botnet• Communication between attacker
and zombies goes via centralized server– Classical communication method
IRC (Internet Relay Chat)Centralized server
31
Centralized botnet topologies
• Centralized topology can be represented in different shapes.• The exact organization of botnet depends on the bot operator
– nothing prevents a bot operator to come up with a new topology.
• Often seen topologies:
HierarchicalMulti-serverStar
32
Star topology• Communication is directly between a
single centralized server and ALL zombies.
• When new machine is infected, it is preconfigured to contact the server to announce its membership.
• Pros: Low latency – Each zombie is issued commands
directly from the server.
• Cons: Low resilience – Only server needs to be blocked to
neutralize the whole botnet
33
Example
• Koobface– Old variant employed start architecture:
• Zombies connected to C&C server directly
34
Multi-server topology• Similar to start topology• Instead of one server, multiple
servers are used to provide instructions to zombies.
Pros: • Better resilience
– No single point of failure • Geographical distribution of servers
– Communication speed up– More resistant to legal shut downs
Cons:• Requires advance planning
35
Hierarchical topology
• Zombies are generally not aware of the server location
Pros: • Ease of re-sale
– A botnet operator can easily carve off sections of their botnet for lease or resale to other operators.
• Hard to enumerate– Hard to evaluate the size and complexity of
the botnet
Cons: • High latency
– makes some botnet attacks difficult.36
Example - Gumblar• Gumblar’s architecture is not
well studied, fully built on zombies
• Website visitors are infected with the Windows executable, it grabs FTP credentials from the victim machines. The FTP account is then used to infect every webpage on new webserver.
37
Decentralized botnet• P2P (peer-to-peer)
communication– zombies talking to each
other– no central server
Pros: Very high resilience Cons:
– High latency– Difficult for enumeration
38
Hybrid topologies
• High resilience• Low latency
• Example, – Hierarchical P2P– Centralized P2P
Centralized Peer-to-peer
39
Storm botnet
• A three-level self-organizing hierarchy:– master servers– proxy bots
• transfers traffic between workers and master servers.
– worker bots• responsible for sending
the spam, proxy bots
• Once a Storm binary is downloaded, an infected host might become a worker bot (if not reachable from the Internet) or a proxy
40
Detection
• Complicated organization of botnets & variety of cover-up techniques make detection of botnets challenging
Part 4 – How do they hide?
43 /
15
Outline
44
45
EncryptionBotnet malware use encryption techniques to avoid being detected by signature-based Intrusion detection system
Matched
46
Snort Example
Without encryption, Snort can successfully detect attack:
12/30-22:59:59.368544 192.168.1.92:138 -> 192.168.1.255:138 UDP TTL:64 TOS:0x0 ID:33092 IpLen:20 DgmLen:234 Len: 214 ..l....F...... EEEBEGEGFJCACACACACACACACACACAAA. ABACFPFPENFDECF CEPFHFDEFFPFPACAB..SMB%..............................&.......... .........&.V.........7.\MAILSLOT\BROWSE.......METALGODS......... ......U.DAFFY. =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
alert udp $EXTERNAL_NET any -> 192.168.1.255 138 (msg:"SAMBA server identified on local subnet!"; content: "SMB"; content: "MAILSLOT";)
[**] [1:0:0] SAMBA server identified on local subnet! [**] 01/06-02:21:23.465726 192.168.1.92:138 -> 192.168.1.255:138 UDP TTL:64 TOS:0x0 ID:64503 IpLen:20 DgmLen:262 Len: 242
PacketWithout encryption
Snort Rule
Snort Alert
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Snort Example
Snort cannot detect attack from encrypted traffic:
12/30-22:59:59.368544 192.168.1.92:138 -> 192.168.1.255:138 UDP TTL:64 TOS:0x0 ID:33092 IpLen:20 DgmLen:234 Len: Li5sLi4uLkYuLi4uLi4gRUVFQkVHRUdGSkNBQ0FDQUNBQ0FDQUNBQ0FDQUNBQUEuIEFCQUNGUEZQRU5GREVDRiBDRkNBQ0FDQUNBQ0FDQUNBQ0FDQUVBGSEZERUZGUEZQQUNBQi4uU01CJS4uLi4uLi4uLi4uLg== =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
alert udp $EXTERNAL_NET any -> 192.168.1.255 138 (msg:"SAMBA server identified on local subnet!"; content: "SMB"; content: "MAILSLOT";)
Encrypted Packet
Snort Rule
48
49
Fast Flux
IP addresses that are rotated in seconds against the same domain.
For example:
[QUESTION] Website name:
www.lijg.ru
[ANSWER] IP Addresses:www.lijg.ru 68.124.161.76www.lijg.ru 69.14.27.151www.lijg.ru 70.251.45.186www.lijg.ru 71.12.89.105www.lijg.ru 71.235.251.99www.lijg.ru 75.11.10.101www.lijg.ru 75.75.104.133www.lijg.ru 97.104.40.246www.lijg.ru 173.16.99.131…………………
50
Advantages for the attacker
Simplicity- Only one suitably powerful backend server (or mothership) host is
needed to serve the master content and DNS information.
Resilience- A layer of protection from ongoing investigative response or legal action
Extend the operational lifespan of the critical backend core servers that arehidden by the front-end nodes
51
An Example of Fast Flux
http://old.honeynet.org/papers/ff/index.html
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Rootkit
A rootkit is a tool that is designed to hide itself and other processes, data, and/or activity on a system
To hide what is taking place an attacker wants to:•Survive system restart•Hide processes•Hide services•Hide listening TCP/UDP ports•Hide kernel modules•Hide drivers
54
How Rootkit Works
• Overwrite first few bytes of target function with a jump to rootkit code• Create “trampoline” function that first executes overwritten bytes from original function, then jumps back to original function• When function is called, rootkit code executes• Rootkit code calls trampoline, which executes original function
55
Rootkit Usage Example – Hide process
Process list BEFOR the rootkit is launched. Process list AFTER the rootkit is launched.
Part 5 – What do botnets do?
Botnet Activities
The least damage caused by Botnets: Bandwidth Consumption
Other things:• DDOS attacks• Spam• Click Fraud• Data Theft• Phishing• Mistrustful services
57 / 4
DDOS attacks
e.g. Google.com
ChinaBrazilRussia US
Attacker
58http://en.wikipedia.org/wiki/Denial-of-service_attack
Click Fraud
• Pay per Click (PPC) is an Internet advertising model used on websites in which advertisers pay their host only when an ad is clicked.
• Famous Bots: ClickBot(100k), Bahama Botnet (200k)
59
Click Fraud - FFSearcher
http://blog.trendmicro.com/click-fraud-takes-a-step-forward-with-troj_ffsearch/60
Data Theft
• Accounts for a great deal of botnet activity.• Purpose: Harvesting user data
– Screen captures– Typed data– Files
• Anti-Spyware software– Highly controversial.– Has resulted in
Scareware.61
http://www.antiphishing.org/reports/apwg_report_h1_2009.pdf
Data Theft-Mumba Zeus Botnet
http://avg.typepad.com/files/revised-mumba-botnet-whitepaper_approved_yi_fv-2.pdf 62
Phishing
• A deceptive email/website/etc. to harvest confidential information.
63http://library.thinkquest.org/06aug/00446/Phishing.html
64http://www.antiphishing.org/reports/apwg_report_h1_2009.pdf
Part 6 – How difficult is it to create a botnet?
Botnet business is booming
• The primary reason for rapid botnet evolution is the underground market
• Botnet services has reached a professional level– Software, zombies or even botnet service can be purchased
– Customization & professional support – http://www.hackforums.net/showthread.php?tid=569629– http://www.hackforums.net/showthread.php?tid=507030&highlight=bot– http://www.hackforums.net/showthread.php?tid=611998– http://www.hackforums.net/showthread.php?tid=611678
66
Reality
• To obtain a simple botnet or botnet services DOES NOT require – Great technical knowledge– Special hardware
… unless you’re planning to make it your primary source of income
67
What is needed to create a simple botnet
1. A bot, i.e., a small program that can remotely perform certain functions
2. C&C server
3. A network of zombies
68
Step 1: Creating a bot
• Where to find a bot:– Find a script on the Internet– Purchase a ready-to-go bot
• Prices vary from $5 to $1000 depending on the bot functionality
– Write yourself
69
Step 2: C&C server
• C&C server is simply a powerful computer which will give you direct access to zombies, or if needed will store stolen data.
• For example, to install IRC server– Dedicated computer with installed software (fairly legal)– Buy a domain, since it should be set up as a web server – Hosting - to make the server accessible from the Internet,
it should be hosted by a hosting company
70
Step 3: Creating zombies• Options:
– Purchase/rent a network of zombies– Compromise computers yourself
• Using software packages such as Mpack, Icepack and WebAttacker
• Using your brains
71
Thank You!Thank You!
72
Extra Slides
Social Aspects of Botnets
• Malware in general is written by some, contributed by others and used by many more.
• Incentives– Challenge Seeking (C:H N:L)– Fame Seeking (C:A N:A)– Revenge Seeking (C:? N:L)– Gain Seeking
74
Fight-back
• Centralized C&C– C&C migration– Random Domain Names– E.g. McColo takedown
• Peer-to-peer– New protocols
• SpamThru
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http://gadgets.boingboing.net/2008/11/13/colo-shutdown-takes.html
Botnet Detection
• Every interaction between two entities requires the flow of information.
• This can utilized to detect the interaction.• The problem is that this interaction is generally
obfuscated and mixed with others with similar behaviour.
• Traditionally work in botnet detection has been categorized by either detection methodology (behavioural/signature) or C&C infrastructure.
76
References• The Gumblar system, http://www.securelist.com/en/weblog?
discuss=208187897&return=1• C. Kanich, C. Kreibich, K. Levchenko, B. Enright, G. Voelker, V. Paxson, S.
Savage. Spamalytics: An Empirical Analysis of Spam Marketing Conversion. 15th ACM Conference on Computer and Communications Security 2008, Alexandria, VA, USA.
• The Koobface botnet, http://us.trendmicro.com• Malicious websites,
http://www.ipa.go.jp/security/english/virus/press/201001/E_PR201001.html
• The fast flux techniques, http://old.honeynet.org/papers/ff/index.html
77