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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 Botnets What are they?. In the news….
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Introduction to Botnets Instructors: Ali Shiravi, University of New Brunswick Natalia Stakhanova, University of South Alabama Hanli Ren, University of New Brunswick
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
Introduction Attacker (Botmaster ) • Malwareis 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. Zombies
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
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.
Popular Botnets Propagation Methods Spammed Messages Install Malware Become Bot Worm Social Networking Websites Removable Devices Malicious Websites
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
Propagation Steps Step 1: Click Link Step 2: Link to malicious website Step 3: Download & Run Malware
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.exe ecard.jpg FullVideo.exe Full Story.exe Video.exe Read More.exe FullClip.exe GreetingPostcard.exe MoreHere.exe FlashPostcard.exe GreetingCard.exe ClickHere.exe ReadMore.exe FlashPostcard.exe FullNews.exe NflStatTracker.exe ArcadeWorld.exe Left-right-brain-test.gif
Social Networking Websites e.g. Koobface
Social Networking Websites Koobface Downloader http://us.trendmicro.com
Koobface Spam Messages • A typical KOOBFACE infection starts with a spam sent through: • Facebook • Twitter • MySpace • Other social networking sites http://us.trendmicro.com
Koobface Spam Messages http://us.trendmicro.com
Koobface Spam Messages http://us.trendmicro.com
Koobface Spam Messages http://us.trendmicro.com
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
Malicious Websites e.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/
Traditional botnet Attacker Botnet topology mainly refers to the organization of C&C channels between zombies and an attacker. Your home computer Commands & controls Zombies Infect Attack Victim
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: Star Multi-server Hierarchical
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.
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
Encryption Botnet malware use encryption techniques to avoid being detected by signature-based Intrusion detection system Matched
Snort Example Without encryption, Snort can successfully detect attack: Packet Without encryption Snort Rule Snort Alert
Snort Example Snort cannot detect attack from encrypted traffic: 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 are • hidden by the front-end nodes