The reader is referred here to an earlier article for the basics of sniffer detection. When sniffers are working on switches, the chances of detecting them are higher. In such a scenario the sniffer is not a passive device; it performs certain activities by which it can be detected.
ARP spoofing can be detected using a program called ARP Watch. It is used to monitor the ARP cache of a machine to see if there is duplication. If there is, it could trigger alarms and lead to detection of sniffers. It can be obtained at online.securityfocus.com/data/tools/arpwatch.tar.Z
As is clear from the above sections, one method of sniffing in a switched environment is using ARP spoofing, and the machine that will most probably be ARP spoofed is the gateway. One thing that can be done is to add the MAC address of the gateway permanently to your ARP cache. This can be done by giving the -s flag to the arp command. Read more about this on the arp man page. Alternatively, you could use the /etc/ethers file for placing the MAC addresses of the important machines to prevent spoofing of those machines.
Final words of advice: Use encryption. Switch to SSH and SCP instead of Telnet and FTP.
Sumit Dhar works for SLMsoft.com.
Practical Task Scheduling Deployment
July 20, 2016 12:00 pm CDT
One of the best things about the UNIX environment (aside from being stable and efficient) is the vast array of software tools available to help you do your job. Traditionally, a UNIX tool does only one thing, but does that one thing very well. For example, grep is very easy to use and can search vast amounts of data quickly. The find tool can find a particular file or files based on all kinds of criteria. It's pretty easy to string these tools together to build even more powerful tools, such as a tool that finds all of the .log files in the /home directory and searches each one for a particular entry. This erector-set mentality allows UNIX system administrators to seem to always have the right tool for the job.
Cron traditionally has been considered another such a tool for job scheduling, but is it enough? This webinar considers that very question. The first part builds on a previous Geek Guide, Beyond Cron, and briefly describes how to know when it might be time to consider upgrading your job scheduling infrastructure. The second part presents an actual planning and implementation framework.
Join Linux Journal's Mike Diehl and Pat Cameron of Help Systems.
Free to Linux Journal readers.Register Now!
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