zeek April 2019

zeek@lists.zeek.org

40 participants
33 discussions

by Manju Lalwani

Hi Team, I am working on a Zeek script and would like to understand how can I make Zeek look only for the first ten packets in a tcp session.The first ten packets are enough to fingerprint the traffic I am trying to identify and so would to ensure my script also looks at only the first 10 packets to save processing time. The communication is as follows : There is the initial 3 way handshake and then there are 7 packets with variable lengths and on a non-default destination port/service. So I had to use the tcp_packet event in my script. Is there a better way of doing it ? Using tcp_packet would make my script to check for all tcp packets increasing the load on my zeek system. Please do let me know if you have any suggestions for me on this. Looking forward to your response. Thanks, Manju Lalwani

2 years, 3 months

Extracting packets from a particular connection

by Raghunath, Ananditha - 0557 - MITLL

Hi, I was hoping to understand how Zeek aggregates packets by connection. Is there any documentation that summarizes the approach? Is there a way to extract all the packets that correspond to a particular connection? Thank you, Ananditha Raghunath - 0557 Assistant Staff Cyber Operations and Analysis Technology MIT Lincoln Laboratory ananditha.raghunath(a)ll.mit.edu | 781-981-9035

2 years, 3 months

tcmalloc large alloc

by Rogers, Zach

Hello, We have been seeing some crash reports on some of our nodes, regarding a tcmalloc error. I was wondering if anyone else has seen this before and if anyone has any suggestions on what the cause might be. We are running Zeek 2.6. Here is an example stderr.log output from one of these crashes: ==== stderr.log Myricom: Local timesource listening on p2p2 tcmalloc: large alloc 1329594368 bytes == 0xc701c000 @ 0x7f72a12604ef 0x7f72a1280d56 0x9623cf 0x9623ff 0x8d8c90 0x8d1b79 0x928352 0x92895f 0x928a71 0x9242bd 0x7b5908 0x7ff59f 0x7b535d 0x7b555f 0x7b3a98 0x8c422e 0x8c3a70 0x95d49e 0x95dc16 0x8c33cc 0x8c36f9 0x8c323f 0x8c18be 0x8bef32 0x95d352 0x5c61dd 0x676f75 0x677f1c 0x648a0f 0x914669 0x648ec5 tcmalloc: large alloc 1661992960 bytes == 0x11641c000 @ 0x7f72a12604ef 0x7f72a1280dad 0x9623cf 0x9623ff 0x8d8c90 0x8d1b79 0x928352 0x92895f 0x928a71 0x9242bd 0x7b5908 0x7ff59f 0x7b535d 0x7b555f 0x7b3a98 0x8c422e 0x8c3a70 0x95d49e 0x95dc16 0x8c33cc 0x8c36f9 0x8c323f 0x8c18be 0x8bef32 0x95d352 0x5c61dd 0x676f75 0x677f1c 0x648a0f 0x914669 0x648ec5 /usr/local/bro/share/broctl/scripts/run-bro: line 110: 138751 Killed nohup "$mybro" "$@" Thanks! -- Zach Rogers Lead Security Analyst Security and Network Monitoring Oregon Research & Teaching Security Operations Center (ORTSOC) Phone: 541.737.7723 GPG Fingerprint: ECC5 03A6 7E91 17C6 50C6 8FAC D6A0 8001 2869 BD52

2 years, 5 months

Bro -r using multiple PCAP

by David Decker

Looking to see if anyone has created a script, or if this is an argument to process multiple PCAPS using the bro -r argument. I have it setup to output to JSON currently and change from EPOCH time to normal date/time output, but that is one at a time, and will have multiple. Looking at either a batch script of maybe python but wanted to see if anyone has done this bfore. (Reingest multiple old PCAP files) to get re-ingested. Dave

2 years, 5 months

Newsletter

by Amber Graner

Hi all, We're going to be rolling out a newsletter. Do you have any zeek related news you'd like me to considering adding in? Do you know of any Zeek related jobs? If you have any topics you'd like to suggest please let me know by sending to news(a)zeek.org. I look forward to hearing from you! With gratitude, ~Amber -- *Amber Graner* Director of Community Corelight, Inc 828.582.9469 * Ask me about how you can participate in the Zeek (formerly Bro) community. * Remember - ZEEK AND YOU SHALL FIND!!

2 years, 5 months

Number of CPU cores for 100Gbps

by Woot4moo

My understanding is that 4,000+ CPU cores would be necessary to support this throughput. In the recent meeting from CERN I recall seeing someone describe 200Gbps, which would imply 8,000+ CPU cores. Is this accurate, or am I doing a conversion incorrectly? I am basing this purely on this quote, from https://docs.zeek.org/en/stable/cluster/ “The rule of thumb we have followed recently is to allocate approximately 1 core for every 250Mbps of traffic that is being analyzed. However, this estimate could be extremely traffic mix-specific. It has generally worked for mixed traffic with many users and servers. For example, if your traffic peaks around 2Gbps (combined) and you want to handle traffic at peak load, you may want to have 8 cores available (2048 / 250 == 8.2). ”

2 years, 5 months

- extracted filename with md5

by william de ping

Hi everyone, I want to extract files and have their names include their md5 hash. The problem is that the md5 hashing happens on file_hash event while file extraction occurs on former events such as file_new or file_over_new_connection. Any ideas on how to accomplish this? Thanks B

2 years, 5 months

Deprecation of &persistent

by David Hoelzer

Hello all! TLDR: I'd like to ask that there be some thought given to the deprecation and eventual removal of the &persistent option in favor of Broker data stores. IMHO, there are uses cases where the &persistent attribute is much more attractive and lower overhead than the data store approach. Longer: As you are likely aware, &persistent is now marked deprecated and we expect it to disappear in the next version or two. The recommendation for replacement is the much more robust, SQLite backed, Broker data store. The data store solution is very elegant, though it does seem to require more fiddling than it ought to to get a data store set up. In the long term and when dealing with large amounts of data that must be persistent and synchronized across nodes, this really is a wonderful solution. That said, there seem to me to be some use cases where that is a massive hammer to swing at some very small problems. For example, we have one analysis script that is tracking successful external DNS resolutions. Specifically, it is keeping track of all IPv4 and IPv6 addresses resolved in the last 7 days (&read_expire 7 days) in a set. For all outbound connection attempts, this script generates a notice when the connection involves an external host that never appeared in a DNS answer record. This is quite handy when it comes to locating unauthorized outbound scanning, some C2 behaviors that do not rely on DNS/fast flux sorts of things, fragile configurations of enterprise services, etc. This has been performing quite well for several years now in more than one relatively decent sized networks (100,000+ hosts). For this problem (and others that I can imagine that would take a similar tack - i.e., only storing a set, vector, or other single primitive, rather than a massive record in a table or a table of tables), the &persistent is perfectly "sized." Am I alone in thinking that this feature should be retained *along side of* Broker data stores and potentially documented as recommended for simple primitive data persistence? Thanks! -- ---- David Hoelzer Chief of Operations Enclave Forensics, Inc.

2 years, 5 months

High capture loss for some workers

by Mark Gardner

We are setting up a Zeek cluster consisting of a manager/logger and five sensors. Each node uses the same hardware: - 2.4 GHz AMD Epyc 7351P (16-core, 32-threads) - 256 GB DDR3 ECC RAM - Intel X520-T2 10 Gbps to Arista with 0.5m DAC Configuration: - Arista 7150S hashing on 5-tuple - Gigamon sends to Arista via 4x10 Gbps - Zeek v2.6-167 with AF_Packet - 16 workers per sensor (total: 5x16=80 workers) The capture loss was 50-70% until I remembered to turn off offloading. Now it averages about 0.8%. Except that often 0-4 cores in a 1 hour summary spike at 60-70% capture loss. There doesn't appear to be a pattern on which core suffers the high loss. Searches for how to identify and fix the reason for such large losses have failed to yield any suggestions for debugging the problem. Suggestions? Mark

2 years, 5 months

Traceback in summary email

by Mark Gardner

I am getting a traceback in the connection summary emails rather than useful information. I didn't have the Python SubnetTree package installed when I built, installed, and first started Zeek but have since installed it on the management/logger and all sensors. I restarted Zeek but am still seeing the traceback. Suggestions on where to look next? Traceback (most recent call last): File "/usr/local/bro/bin/trace-summary", line 22, in <module> import SubnetTree File "/usr/local/bro/lib/broctl/SubnetTree.py", line 21, in <module> _SubnetTree = swig_import_helper() File "/usr/local/bro/lib/broctl/SubnetTree.py", line 20, in swig_import_helper return importlib.import_module('_SubnetTree') File "/usr/lib/python2.7/importlib/__init__.py", line 37, in import_module __import__(name) ImportError: dynamic module does not define init function (init_SubnetTree)

2 years, 5 months

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zeek April 2019