Ever want to run a persistent tcpdump process to monitor something you’re never online at the right time to catch? Sure you can just run tcpdump outputting to a file forever, but you will probably have limited disk space. A busy server can run through a ton of drive space fast! Maybe you’ve gone as far as using bash or perl to script tcpdump log rotation. However you can now rejoice in the knowledge that tcpdump can do this for you:
tcpdump -i br0 port 80 -s 0 -vvv -C 1 -W 5 -w /tmp/whatever.pcap
In that example your’e going to capture on interface ‘br0’ for port ’80’ and make ‘-C 1’ 1MB log files and keep ‘-W 5’ 5 of them which will automatically rotate. Adjust as needed depending on the storage capacity and throughput of your server!
Site’s now hosted on a new server with upgraded specs. Should be some improvements in responsiveness. More content coming soom!
Today I ran a workshop with our newest network administrators; Our topic was denial of service mitigation. We currently utilize Arbor Peakflow Threat Management System to detect and scrub inbound attacks. Arbor is a phenomenal system capable of amazing performance. With the right tuning, templates and bandwidth it’s virtually handsfree. However some motivated attackers manage to sneak through occasionally. My goal was to educate our team on the nature of denial of service attacks and manual operation of the Arbor system. The ultimate goal was sparking interest in security while ensuring our newest members can think on their feet when Arbor’s magic runs out. Through the workshop I escalated my attacks in terms of difficulty rather than volume. I didn’t stick to a concrete lesson plan when it came to crafting the attacks, instead I adapted my attacks to their reactions much like a real determined attacker would. Continue reading
Posted in Bash One-Liners, Linux Guides, Network Security
Tagged arbor networks, arbor peakflow, arbor peakflow threat management system, arbor tms, attack vector, blacklist, datagram, ddos, ddos mitigation, ddos protectiond, ddos scrubbing, denial of service, distributed denial of service, dos, dos scrubbing, drdos, flood protection, hping, hping2, hping3, netadmin, netops, network administration, packet, payload, peakflow, stateless protocol, synflood, threat management system, udp flood, udp packet, udpflood, whitelist, zombie detection
I’ve encountered this issue several times on windows VMs (sadly need a few still) where modern versions of Windows, i.e. Windows 8 will occasionally prevent you from deleting a directory. One was a directory an installer created, in this case Open Office, which was not cleaned up due to a VM crash during the install process. The file was showing ownership set to my regular user account. However the user could not delete the file, Windows would simply say I have to get permission from myself to delete it. I tried logging in as Administrator and assigning ownership to Administrator via the Advanced menu in the Security tab of the file properties. At this point windows would still tell me I need the non-Admin user’s permission to delete it (wtf, I’m admin…) and would now tell the regular user I need Admin’s permission to delete it. Basically windows has become the operating system equivalent of the DMV or any other government operation with an added touch of dementia.
I found the following commands as Administrator from command prompt solved my issue:
takeown /f "C:\Users\myusername_000\Desktop\OpenOffice 4.1.1 (en-US) Installation Files" /r /d y
icacls "C:\Users\myusername_000\Desktop\OpenOffice 4.1.1 (en-US) Installation Files" /grant administrators:F /t
After that I was able to right click and delete the directory without issue as Administrator. Overall it’s pretty crappy that windows can’t work out file ownership/permissions. This is something that has worked on Unix and Linux, without issue, since as long as most of us can remember.
Posted in Misc Technology
Tagged can't delete, can't delete file, can't delete files, can't delete folder, file permissions, uac sucks, windows 8, windows 8 sucks, windows can't delete, windows can't delete folder, windows sucks
I’ve struggled to improve Samba (SMB) performance between my Mac Pro (Late 2013) running OS X Yosemite 10.10.2 and my CentOS 6.6 Linux server. The server has a large ZFS share with all my backups and archives as well as various KVM instances running off SSDs. My Mac Pro absolutely must access that ZFS share reliably and it would be nice if my two Mac Books were able to as well. I have a lot of experience with SMB and I’ve never had much trouble working with Linux servers and Windows clients. On OS X however I’ve never had any luck, the connectivity is slow, buggy and generally unreliable.
Tonight I decided to install Netatalk, latest version on my CentOS server from source code. Below is the documentation of the procedure I followed and any outcome I was able to document.
Posted in Linux Guides, OS X
Tagged afp, afpd, apple filing protocol, centos, linux, mac, netatalk, nfs, os x, osx, samba, san, smb, storage, yosemite, zfs
The 1990s truly launched us into information age as we know it today. The world saw the internet reach critical mass, it’s entrepreneurs, investors and the virtual gold rush known as the dot-com bubble. The internet was told to have unfathomable wealth for those who could attain it. Unfortunately few entrepreneurs understood the internet and how it can be monetized.
This leads us to today. A world where being disconnected from the internet is seen as a human rights violation. A truly remarkable market is before us. A market with real tangible fortunes being made. So what does this have to do with the humble sales rep?
Working on updating some ServerTech CDU firmware today I found that they wouldn’t connect to my fresh new FTP server. I checked my firewall, I checked my server log, and saw that they weren’t authenticating correctly:
Aug 16 16:24:56 bouncer vsftpd: pam_unix(vsftpd:auth):
authentication failure; logname= uid=0 euid=0 tty=ftp
ruser=ftpupdate rhost=10.40.2.31 user=ftpupdate
A few months ago we all saw the dramatic boom in NTP reflection attacks. These attacks exceeded DNS reflection that was so common before it. At the time I was personally experiencing consistent 10 to 40+ Gbps attacks. After a while they started to die down in frequency and volume. I still see many NTP reflection attacks, but in the last week I observed a large influx of SNMP based reflection attacks. It’s not the first time I’ve seen SNMP reflection in the wild, I see a few SNMP attacks every couple of months. Personally I’ve expected SNMP attacks to increase due to the large payloads generated by poorly secured SNMP daemons. Continue reading
Posted in Network Security
Tagged amplification attack, ddos, denial of service, dns reflection, drdos, forged packet, ntp reflection, reflection attack, snmp reflection, spoofed packet, stateless protocol, udp stateless
Hey guys, not a long post today, but thought I’d throw out an easy little tip. I was installing some KVM guests on a CentOS 6.5 storage server and needed a VNC client for my OS X desktop. Found something neat that some of you may already know, but if not, it’s pretty cool. Continue reading