How secure is your network?

David Dodd

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In a switched network environment packets are sent to their destination port by MAC address. This requires that hardware be able to create and maintain a table associating MAC addresses to ports. In a switched environment packets are only sent to devices that they are meant for. Even in this switched environment there are ways to sniff other devices' packets. One such way is to spoof your MAC address and poison the arp table. Since there is no state information about ARP traffic kept, as it's a simple protocol, the arp cache can be overwritten (unless the entry was explicitly marked as permanent). Arp cache poisoning puts the attacker in position to intercept communications between the two computers. Computer A believes it is communicating with Computer B, but because of the poisoned arp table, the communication actually goes to the attacker's computer. The attacker ... (more)

Intruder Detection with tcpdump

To capture, parse, and analyze traffic tcpdump is a very powerful tool. To begin a basic capture uses the following syntax. tcpdump -n –i -s -n      tells tcpdump to not resolve IP addresses to domain names and port numbers to service names. -I       tells tcpdump which interface to use. -s      tells tcpdump how much of the packet to record. I used 1515 but 1514 is sufficient for most cases. If you don’t specify a size then it will only capture the first 68 bytes of each packet. A snaplen value of 0 which will use the required length to ... (more)

Malware Analysis | Part 2

In a previous article [1], I described how to obtain a memory image from a Windows computer that would allow forensic analysis. I briefly discussed using F-Response TACTICAL [2] to get the memory image, and then Volatility [3] and Mandiant Redline [4] for further investigation. In this paper, I dive more deeply into Redline and Volatility. To begin, I review a raw memory dump of a known malware variant (see the "Malware Image" box) with Mandiant Redline. After firing up Redline, I chose By Analyzing a Saved Memory File under Analyze Data and browsed to the location of the memory... (more)

Planning, Scoping and Recon Techniques

The purpose of this article is to describe some tools and techniques in performing the planning, scoping, and recon portion of a penetration test. In covering these tools and techniques the reader will learn how to use them to find vulnerabilities in their organization and help improve security posture. Some other names for this first phase of penetration testing are; OSINT (Open Source Intelligence), Footprinting, Discovery, and Cyberstalking. Introduction During reconnaissance we'll gather information from public sources to learn about the target and try to find what is importan... (more)

Capture File Filtering with Wireshark

Intrusion detection tools that use the libpcap C/ C++ library [1] for network traffic capture (such as Snort [2] and Tcpdump [1]) can output packet capture information to a file for later reference. The format of this capture file is known as pcap. By capturing packet data to a file, an investigator can return later to study the history of an intrusion attempt – or to turn up other important clues about clandestine activity on the network. Of course, the traffic history data stored in a pcap file is much too vast to study by just viewing the file manually. Security experts use spe... (more)