介紹到今天頂面Botnet攻擊

由 Corey Nachreiner， CISSP網絡證券分析人員， WatchGuard技術

[編者按： 這篇文章補充在錄影系列的顯示的攻擊名單第2部分， Malware分析： Botnets。 「Malware分析： Botnets，分開botnet的一個小子集在行動攻擊的2個″展示。 這篇文章填好子集與更多在bot牧者的武庫攻擊共同地發現。 LiveSecurity訂戶能發現錄影，免費，在我們 錄影講解 頁。 –斯科特]

您經常將聽見botnets被描述作為「黑客的瑞士軍刀」。 正瑞士軍刀可能來以刀片、剪刀和螺絲刀瘋狂的品種，馬胃蠅蛆來以允許bot牧者發射攻擊的許多不同的類型的許多盤剝和命令。

從編碼bot客戶作為計時，并且技巧，多數攻擊者在網上地下買bot代碼。 普遍的惡意馬胃蠅蛆包括Phatbot， Agobot和在我們的錄影顯示的那個， Rxbot。 這些bot客戶使用模件代碼，因此，如果bot牧者不愛命令他的bot提議，他簡單地增加新的。 為例子，讀。

什麼更好比蛇神和發送同樣的消息到多個新聞組配對？

Bot牧者共同地支持他們的馬胃蠅蛆作為巨大的發送同樣的消息到多個新聞組中轉。 多麼巨大？ 根據一項最近研究由Commtouch， 87%所有電子郵件被送在互聯網在2006年期間是發送同樣的消息到多個新聞組。 這種e破爛物引起了1700年太字節(1,700,000,000兆字節)每天網絡通行。 Botnets引起了85%那發送同樣的消息到多個新聞組，不需要的郵件潮汐。

多數bot代碼來以至少幾個命令使兜售信息更加容易。 一些馬胃蠅蛆為兜售信息具體地甚而被優選。 使用Phatbot的bot牧者能發出指令 harvest.emails 收集每封電子郵件在受害者的計算機。 如果Phatbot牧者的botnet包括數以萬計受害者機器，他可能迅速和容易地建立gi-normous電子郵件名單以後發送同樣的消息到多個新聞組。

Agobot為兜售信息被定做。 它甚而包括它自己的SMTP引擎，以便它可能直接地發送同樣的消息到多個新聞組。 它的電子郵件兜售信息命令允許Agobot牧者告訴每一個他的受害者的計算機：

• 下載電子郵件名單發送同樣的消息到多個新聞組
• 下載一個模板電子郵件派出
• 派出消息的開始使用許多另外電子郵件同時穿線
• 開始并且停止發送同樣的消息到多個新聞組，當指示時。

bot在我們的錄影， Rxbot，沒有被認為兜售信息bot。 然而，甚而它包含允許bot牧者從所有他的蛇神受害者送電子郵件的一個基本的命令。

I’m hiding behind my SOCKS

Many bots include a SOCKS server. SOCKS (an abbreviation for sockets) is a networking protocol designed to pass TCP traffic through a proxy server. In other words, if a client wanted to visit www.google.com using SOCKS, the client would send its request to a SOCKS server instead of to Google directly. The SOCKS server forwards that request to Google and returns the response to the client. However, to Google it looks as though the request came from the SOCKS server, not the actual client.

Bot herders love to use the SOCKS proxy to spam. A bot master simply enables the SOCKS proxy on one of his bots, then redirects his SOCKS-compatible, mass emailing program to the IP address of that bot. This causes the email program to send email using that bot as a relay. If an anti-spam program blacklists the bot’s IP address, the herder activates the SOCKS proxy on another bot, and his spam seems to originate from a new, clean IP address.

Furthermore, the bot herder can use a SOCKS proxy to anonymize just about any network traffic. And in Rxbot, for instance, activating the SOCKS proxy is simple: one six-letter command initiates all those anonymizing benefits.

Some bots have a Man-in-the-Middle

Bots also help herders launch Man-in-the-Middle (MitM) attacks. Most bots come with commands that allow their creators to redirect network traffic any way they like. For instance, a bot herder could tell a bot to redirect all its web traffic to his computer. Then, every time the unwitting victim (whose machine is hosting that bot) browses the Web, the attacker sees the traffic before forwarding it to its intended destination. This is one way bot masters capture sensitive information or steal login credentials.

Rxbot comes with the .redirect command. Herders can use this command to forward the network traffic destined for any TCP port, to any IP address they choose. Phatbot comes with additional redirect commands that allow it to forward GRE traffic, the special protocol used in establishing PPTP VPN connections. These examples merely hint at what a bot herder can accomplish with redirects.

Click Fraud and Poll Manipulation

Nowadays, the lure of illegal easy money motivates most bot herders. Our video shows how crooks can force their bots to click on revenue-generating Google ad words. As another example, Rxbot has a simple-yet-effective .visit command. If you send your bots this command, followed by a URL, they silently visit that URL. Here, silently is a technical term meaning the bot victim will not see her computer visit the URL. The visit happens in the background, without any web browser involvement. So, imagine you have 100,000 bots. With one command you could easily force all those bots to visit an online poll, vote, or game. If you wanted ToneDeaf UglyDork to win American Idol, you could command all your bots to visit the American Idol voting page and submit a vote. Since every vote would come from a different IP address, the results would look legitimate. And if the flaws in American e-voting aren’t fixed before 2008, bots just might elect ToneDeaf UglyDork as President, too.

Spam + IM = SPIM

Many IRC bots today have Instant Messenger (IM) and Peer-to-Peer (P2P) components in their attack arsenal. For instance, some bots allow you to send spam to IM channels (nicknamed SPIM ). Attackers commonly send malicious files or URLs to IM users, hoping to infect them with malware. Some bots incorporate commands that allow the bot herder to send these types of IM messages to his bots’ IM buddies. If those buddies then visit the URL or execute an attached file, they get infected with the herder’s bot and become minions in his botnet.

Some bots offer similar commands that help them spread via P2P applications. For instance, Agobot spreads by placing copies of itself in the share directories used by many popular P2P programs such as Kazaa and Limewire. The bot gives its file an enticing name, such as the title of a movie still in theaters. When someone downloads and runs this malicious trojan, their computer becomes another zombie.

Is it just me, or does it smell like bots in here?

In the video, we mentioned that many bots come with packet sniffers. Packet sniffers allow a bot master to see all of the network traffic that passes by his bots, and sometimes all the traffic that passes within the bot victim’s network as well. Attackers can learn a lot by sniffing a network. For instance, a bot herder might capture cleartext logins or see web cookies. They could even passively enumerate your infected network.

Agobot comes with some very advanced packet sniffing capabilities. Rather than sniffing and reporting every single packet, which creates volumes of junk for the herder to parse, Agobot allows a herder to sniff for specific strings or types of traffic. For example, you can command Agobot to capture all the web cookies it sees passing over a network. You can also specifically tell it to only sniff FTP, or IRC logins. In short, if something passes over a network in clear text, Agobot’s sniffing can pinpoint it.

Stay as sharp as the crooks

In our video and this article, we’ve listed the most common “Swiss Army blades” used in bots today. Since botnets are evolving fast, bots could have all-new blades tomorrow. For now, you can protect yourself best by understanding the threat — and following the defense measures we outline in “Malware Analysis: Botnets, Part 3.” Look for it on our Video Tutorials page beginning 17 October, 2007. #