Introduction to Botnets Instructors: Ali Shiravi, University of New Brunswick Natalia Stakhanova,...

transcript

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

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.

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

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.

Botnet Infection Stages - Centralized

Part 2 – How does a botnet operate?

Popular Botnets Propagation MethodsSpammed Messages

Social Networking Websites

Malicious Websites

Install MalwareBecome Bot

Removable Devices

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

Spammed Messages

Storm Botnet

Step 1: Click Link

Step 2:Link to malicious website

Step 3:Download & Run Malware

Propagation Steps

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

Social Networking Websitese.g. Koobface

Social Networking WebsitesKoobface Downloader

http://us.trendmicro.com

Koobface Spam MessagesA typical KOOBFACE infection starts with a spam sent through:• Facebook• Twitter• MySpace• Other social networking sites

Koobface Spam Messages

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.

Malicious Websitese.g. Gumblar Zeus

Malicious Websites

http://www.ipa.go.jp/security/english/virus/press/201001/E_PR201001.html

Gumblar Compromised Website

The malicious script embedded in the website.

http://www.van-manen.info/weblog/2010/02/gumblar-virus-infecteert-microsoft-website/

Zeus Malware Download

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.

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.

Centralized botnet• Communication between attacker

and zombies goes via centralized server– Classical communication method

IRC (Internet Relay Chat)Centralized server

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

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

Example

• Koobface– Old variant employed start architecture:

• Zombies connected to C&C server directly

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

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.

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

Hybrid topologies

• High resilience• Low latency

• Example, – Hierarchical P2P– Centralized P2P

Centralized Peer-to-peer

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

Detection

• Complicated organization of botnets & variety of cover-up techniques make detection of botnets challenging

Part 4 – How do they hide?

Outline

EncryptionBotnet malware use encryption techniques to avoid being detected by signature-based Intrusion detection system

Matched

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

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

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…………………

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

An Example of Fast Flux

http://old.honeynet.org/papers/ff/index.html

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

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

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)

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

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

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

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

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

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

Thank You!Thank You!

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

Fight-back

• Centralized C&C– C&C migration– Random Domain Names– E.g. McColo takedown

• Peer-to-peer– New protocols

• SpamThru

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.

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

Introduction to Botnets Instructors: Ali Shiravi, University of New Brunswick Natalia Stakhanova,...

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