介绍到今天顶面Botnet攻击

由 Corey Nachreiner， CISSP网络证券分析人员， WatchGuard技术

[编者按： 这篇文章补充在录影系列的显示的攻击名单第2部分， Malware分析： Botnets。 “Malware分析： Botnets，分开botnet的一个小子集在行动攻击的2个″展示。 这篇文章填好子集与更多在bot牧者的武库攻击共同地发现。 LiveSecurity订户能发现录影，免费，在我们 录影讲解 页。 –斯科特]

您经常将听见botnets被描述作为“黑客的瑞士军刀”。 正瑞士军刀可能来以刀片、剪刀和螺丝刀疯狂的品种，马胃蝇蛆来以允许bot牧者发射攻击的许多不同的类型的许多盘剥和命令。

从编码bot客户作为计时，并且技巧，多数攻击者在网上地下买bot代码。 普遍的恶意马胃蝇蛆包括Phatbot， Agobot和在我们的录影显示的那个， Rxbot。 这些bot客户使用模件代码，因此，如果bot牧者不爱命令他的bot提议，他简单地增加新的。 为例子，读。

什么更好比蛇神和发送同样的消息到多个新闻组配对？

Bot牧者共同地支持他们的马胃蝇蛆作为巨大的发送同样的消息到多个新闻组中转。 多么巨大？ 根据一项最近研究由Commtouch， 87%所有电子邮件被送在互联网在2006年期间是发送同样的消息到多个新闻组。 这种e破烂物引起了1700年太字节(1,700,000,000兆字节)每天网络通行。 Botnets引起了85%那发送同样的消息到多个新闻组，不需要的邮件潮汐。

多数bot代码来以至少几个命令使兜售信息更加容易。 一些马胃蝇蛆为兜售信息具体地甚而被优选。 使用Phatbot的bot牧者能发出指令 harvest.emails 收集每封电子邮件在受害者的计算机。 如果Phatbot牧者的botnet包括数以万计受害者机器，他可能迅速和容易地建立gi-normous电子邮件名单以后发送同样的消息到多个新闻组。

Agobot为兜售信息被定做。 它甚而包括它自己的SMTP引擎，以便它可能直接地发送同样的消息到多个新闻组。 它的电子邮件兜售信息命令允许Agobot牧者告诉每一个他的受害者的计算机：

• 下载电子邮件名单发送同样的消息到多个新闻组
• 下载一个模板电子邮件派出
• 派出消息的开始使用许多另外电子邮件同时穿线
• 开始并且停止发送同样的消息到多个新闻组，当指示时。

bot在我们的录影， Rxbot，没有被认为兜售信息bot。 然而，甚而它包含允许bot牧者从所有他的蛇神受害者送电子邮件的一个基本的命令。

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. #