Bot detection methods that rely on deep packet in- spection (DPI) can be foiled by encryption. Encryption, however, increases entropy. This paper investigates whether adding high- entropy detectors to an existing bot detection tool that uses DPI can restore some of the bot visibility. We present two high-entropy classifiers, and use one of them to enhance BotHunter. Our results show that while BotHunter misses about 50% of the bots when they employ encryption, our high-entropy classifier restores most of its ability to detect bots, even when they use encryption.
This work is advised by Christos Papadopolous and Dan Massey at Colorado State University.
Visualization of low-rate periodicity, before and after installation of a keylogger. [Bartlett11a, figure 3]The paper “Low-Rate, Flow-Level Periodicity Detection”, by Genevieve Bartlett, John Heidemann, and Christos Papadopoulos is being presented at IEEE Global Internet 2011 in Shanghai, China this week. The full text is available at http://www.isi.edu/~johnh/PAPERS/Bartlett11a.pdf.
The abstract summarizes the work:
As desktops and servers become more complicated, they employ an increasing amount of automatic, non-user initiated communication. Such communication can be good (OS updates, RSS feed readers, and mail polling), bad (keyloggers, spyware, and botnet command-and-control), or ugly (adware or unauthorized peer-to-peer applications). Communication in these applications is often regular, but with very long periods, ranging from minutes to hours. This infrequent communication and the complexity of today’s systems makes these applications difficult for users to detect and diagnose. In this paper we present a new approach to identify low-rate periodic network traffic and changes in such regular communication. We employ signal-processing techniques, using discrete wavelets implemented as a fully decomposed, iterated filter bank. This approach not only detects low-rate periodicities, but also identifies approximate times when traffic changed. We implement a self-surveillance application that externally identifies changes to a user’s machine, such as interruption of periodic software updates, or an installation of a keylogger.
The datasets used in this paper are available on request, and through PREDICT.
An expanded version of the paper is available as a technical report “Using low-rate flow periodicities in anomaly detection” by Bartlett, Heidemann and Papadopoulos. Technical Report ISI-TR-661, USC/Information Sciences Institute, Jul 2009. http://www.isi.edu/~johnh/PAPERS/Bartlett09a.pdf
Abstract: It is well known that spam bots mostly utilize compromised machines with certain address characteristics, such as dynamically allocated addresses, machines in specific geographic areas and IP ranges from AS’ with more tolerant spam policies. Such machines tend to be less diligently administered and may exhibit less stability, more volatility, and shorter uptimes. However, few studies have attempted to quantify how such spambot address characteristics compare with non-spamming hosts.
Quantifying these characteristics may help provide important information for comprehensive spam mitigation.
We use two large datasets, namely a commercial blacklist
and an Internet-wide address visibility study to quantify address characteristics of spam and non-spam networks. We find that spam networks exhibit significantly less availability and uptime, and higher volatility than non-spam networks. In addition, we conduct a collateral damage study of a common practice where an ISP blocks the entire /24 prefix if spammers are detected in that range. We find that such a policy blacklists a significant portion of legitimate mail servers belonging to the same prefix.
The paper “Correlating Spam Activity with IP Address Characteristics” (available at PDF Format) was accepted and presented at Global Internet 2010. The focus of this paper is to quantify the collateral damage (legitimate mail servers incorrectly blacklisted) caused by the practice of blocking /24 address blocks based on the presence of spammers. The paper also revisits the differences in IP address characteristics and domain names between spammers and non-spammers.
From the abstract:
It is well known that spam bots mostly utilize compromised machines with certain address characteristics, such as dynamically allocated addresses, machines in specific geographic areas and IP ranges from AS’ with more tolerant spam policies. Such machines tend to be less diligently administered and may exhibit less stability, more volatility, and shorter uptimes. However, few studies have attempted to quantify how such spam bot address characteristics compare with non-spamming hosts. Quantifying these characteristics may help provide important information for comprehensive spam mitigation.
We use two large datasets, namely a commercial blacklist and an Internet-wide address visibility study to quantify address characteristics of spam and non-spam networks. We find that spam networks exhibit significantly less availability and uptime, and higher volatility than non-spam networks. In addition, we conduct a collateral damage study of a common practice where an ISP blocks the entire /24 prefix if spammers are detected in that range. We find that such a policy blacklists a significant portion of legitimate mail servers belonging to the same prefix.
Citation: Chris Wilcox, Christos Papadopoulos, John Heidemann. Correlating Spam Activity with IP Address Characteristics. Proceedings of the IEEE Global Internet Conference, San Diego, CA, USA, IEEE. March, 2010.
![Visualization of low-rate periodicity, before and after installation of a keylogger. [Bartlett11a, figure 3]](http://ant.isi.edu/blog/wp-content/uploads/2011/04/Bartlett11a_icon.png){kind=icon}