kflowd runs as agent on Linux endpoints to monitor processes via eBPF kernel subsystem for filesystem and TCP and UDP networking events, enabling immediate threat and anomaly detection on suspicious activities.
Advanced non-ebpf related features such as DNS, HTTP and SYSLOG application message decoding, checksum calculation for virus detection, process and file versioning for vulnerability detection and file device, network interface and user-group identification for files and processes can be enabled via open-binary plugin modules.
Pre-built kflowd and kflowd-plugins packages can be downloaded for quick installation from the Releases section.
If you would like to join our community Slack channel please send an email to [email protected] to receive an invitation. You can also contact us directly at [email protected] for any questions.
kflowd contains an eBPF program running in kernel context and its control application running in userspace.
The eBPF program traces kernel functions to monitor processes based on file system and networking events. Events are aggregated into records and submitted into a ringbuffer where they are polled by the userspace control application. All Records are enriched with process information and then converted into a message in JSON output format.
Final messages are printed to stdout console and can be sent via UDP protocol to specified hosts for ingestion in a security data pipeline.
kflowd runs on Linux kernels 5.10+ and is built with the libbpf+CO-RE (Compile-Once-Run-Everywhere) eBPF development toolchain using BTF (BPF Type Format) to allow portability by avoiding dependencies on differences in kernel headers between kernel versions on deployment.
kflowd outputs JSON messages generated for each record of aggregated file system and TCP, UDP networking events and optionally DNS, HTTP and SYSLOG application messages in the formats as shown in the following examples:
Filesystem Record
{
"InfoSequenceNumber": 1,
"InfoTimestamp": "Thu, Apr 04 2024 15:34:35.643031330 UTC",
"InfoMonitor": "filesystem",
"InfoHostName": "dev.kflow.co",
"InfoHostIP": "38.110.1.24",
"InfoSystem": "Linux",
"InfoKernel": "6.1.0-10-amd64",
"InfoVersion": "kflowd-v0.9.1",
"InfoUptime": 21.262713426,
"ProcParent": "sshd",
"Proc": "sftp-server",
"ProcVersion": "1:9.2p1-2+deb12u1",
"ProcUser": "dirk",
"ProcGroup": "dirk",
"ProcPPID": 183546,
"ProcPID": 183547,
"ProcTID": 183547,
"ProcUID": 1002,
"ProcGID": 1002,
"ProcAge": 2.408293862,
"FilePath": "/home/dirk/",
"File": "malware",
"FileVersion": "0.9",
"FileMode": "regular",
"FileEventCount": 4,
"FileEvents": {
"OPEN": 1,
"MODIFY": 2,
"CLOSE_WRITE": 1
},
"FileEventsDuration": 0.811829334,
"FileInode": 19567988,
"FileInodeLinkCount": 1,
"FileDevice": "902h:/dev/md2:/:ext4",
"FilePermissions": "0755/-rwxr-xr-x",
"FileUser": "dirk",
"FileGroup": "dirk",
"FileUID": 1002,
"FileGID": 1002,
"FileSize": 41,
"FileSizeChange": 41,
"FileAccessTime": "Thu, Apr 04 2024 15:12:01.435718956 UTC",
"FileStatusChangeTime": "Thu, Apr 04 2024 15:34:35.154106191 UTC",
"FileModificationTime": "Thu, Apr 04 2024 15:34:35.154106191 UTC",
"FileModificationTimeChange": 0.327993681,
"FileMD5": "96760f46bd29ba986279f22bed9839f5",
"FileSHA256": "72c58c2d02ae3a87f521594373433b7d05477c4994fc0ab4376827cadb29ba7e"
}
UDP + DNS Networking Record
{
"InfoSequenceNumber": 2,
"InfoTimestamp": "Thu, Apr 04 2024 15:39:11.463732866 UTC",
"InfoMonitor": "socket",
"InfoHostName": "dev.kflow.co",
"InfoHostIP": "38.110.1.24",
"InfoSystem": "Linux",
"InfoKernel": "6.1.0-10-amd64",
"InfoVersion": "kflowd-v0.9.1",
"InfoUptime": 23.972984597,
"ProcParent": "bash",
"Proc": "curl",
"ProcVersion": "7.45.2-3",
"ProcUser": "dirk",
"ProcGroup": "dirk",
"ProcPPID": 199853,
"ProcPID": 199856,
"ProcTID": 199857,
"ProcUID": 1002,
"ProcGID": 1002,
"ProcAge": 0.044454620,
"SockProtocol": "UDP",
"SockRole": "CLIENT",
"SockState": "UDP_ESTABLISHED",
"SockFamily": "AF_INET",
"SockLocalIP": "38.110.1.24",
"SockLocalPort": 56664,
"SockRemoteIP": "8.8.4.4",
"SockRemotePort": 53,
"SockTxInterface": "4:enp5s0:0c:c4:7a:88:84:c2",
"SockTxPackets": 2,
"SockTxDuration": 0.000048490,
"SockTxBytes": 52,
"SockTxInterface": "4:enp5s0:0c:c4:7a:88:84:c2",
"SockRxPackets": 2,
"SockRxPacketsQueued": 0,
"SockRxPacketsDrop": 0,
"SockRxPacketsFrag": 0,
"SockRxDuration": 22.475134750,
"SockRxBytes": 155,
"SockRxTTL": 125,
"SockAge": 0.043689149,
"App": "DNS",
"AppTxDns": [{
"_Timestamp": 0.000001177,
"TransactionId": 56864,
"OpCode": "QUERY",
"Flags": ["RD"],
"ResourceRecords": [
["A", "kflow.co"]
]
},
{
"_Timestamp": 0.000048627,
"TransactionId": 52515,
"OpCode": "QUERY",
"Flags": ["RD"],
"ResourceRecords": [
["AAAA", "kflow.co"]
]
}],
"AppRxDns": [{
"_Timestamp": 0.037965555,
"TransactionId": 52515,
"ResponseCode": "NOERROR",
"Flags": ["QR", "RD", "RA"],
"AnswerCount": 0,
"ResourceRecords": []
},
{
"_Timestamp": 0.043688644,
"TransactionId": 56864,
"ResponseCode": "NOERROR",
"Flags": ["QR", "RD", "RA"],
"AnswerCount": 2,
"ResourceRecords": [
["A", "kflow.co", 600, "IN", "15.197.142.173"],
["A", "kflow.co", 600, "IN", "3.33.152.147"]
]
}]
}
TCP + HTTP Networking Record
{
"InfoSequenceNumber": 3,
"InfoTimestamp": "Thu, Apr 04 2024 15:39:11.928989997 UTC",
"InfoMonitor": "socket",
"InfoHostName": "dev.kflow.co",
"InfoHostIP": "38.110.1.24",
"InfoSystem": "Linux",
"InfoKernel": "6.1.0-10-amd64",
"InfoVersion": "kflowd-v0.9.1",
"InfoUptime": 24.873001288,
"ProcParent": "bash",
"Proc": "curl",
"ProcVersion": "7.45.2-3",
"ProcUser": "dirk",
"ProcGroup": "dirk",
"ProcPPID": 199853,
"ProcPID": 216998,
"ProcTID": 216998,
"ProcUID": 1002,
"ProcGID": 1002,
"ProcAge": 0.114196829,
"SockProtocol": "TCP",
"SockRole": "CLIENT",
"SockState": "TCP_CLOSE",
"SockFamily": "AF_INET",
"SockLocalIP": "38.110.1.24",
"SockLocalPort": 43302,
"SockRemoteIP": "15.197.142.173",
"SockRemotePort": 80,
"SockTxInterface": "4:enp5s0:0c:c4:7a:88:84:c2",
"SockTxDataPackets": 1,
"SockTxPackets": 6,
"SockTxPacketsRetrans": 0,
"SockTxPacketsDups": 0,
"SockTxFlags": {
"SYN": 1,
"ACK": 3,
"PSH-ACK": 1,
"FIN-ACK": 1
},
"SockTxDuration": 0.057274799,
"SockTxBytes": 72,
"SockTxBytesAcked": 74,
"SockTxBytesRetrans": 0,
"SockTxRTO": 51,
"SockTxInterface": "4:enp5s0:0c:c4:7a:88:84:c2",
"SockRxDataPackets": 1,
"SockRxPackets": 4,
"SockRxPacketsQueued": 0,
"SockRxPacketsDrop": 0,
"SockRxPacketsReorder": 0,
"SockRxPacketsFrag": 0,
"SockRxFlags": {
"SYN-ACK": 1,
"ACK": 1,
"PSH-ACK": 1,
"FIN-ACK": 1
},
"SockRxDuration": 0.057197399,
"SockRxBytes": 342,
"SockRxTTL": 185,
"SockRTT": 0.000450625,
"SockAge": 0.057344028,
"App": "HTTP",
"AppTxHttp": [{
"_Timestamp": 0.000876589,
"_Method": "GET",
"_Url": "/",
"_Version": "HTTP/1.1",
"Host": "kflow.co",
"User-Agent": "curl/7.88.1",
"Accept": "*/*"
}],
"AppRxHttp": [{
"_Timestamp": 0.056237469,
"_Version": "HTTP/1.1",
"_Status": 301,
"_Reason": "Moved Permanently",
"Date": "Thu, 04 Apr 2024 15:49:12 GMT",
"Content-Type": "text/html; charset=utf-8",
"Content-Length": "59",
"Connection": "keep-alive",
"Location": "https://kflowd.github.io",
"Server": "ip-10-123-123-119.ec2.internal",
"X-Request-Id": "5c331cbe-fbe1-40ea-ba2b-989691e687a0",
"_Body": "<a href=\"https://kflowd.github.io\">Moved Permanently</a>."
}]
}
UNIX Socket + SYSLOG Record
{
"InfoSequenceNumber": 4,
"InfoTimestamp": "Mon, Sep 16 2024 14:30:19.409100980 UTC",
"InfoMonitor": "socket",
"InfoHostName": "dev.kflow.co",
"InfoHostIP": "38.110.1.24",
"InfoSystem": "Linux",
"InfoKernel": "6.1.0-10-amd64",
"InfoVersion": "kflowd-v0.9.11",
"ProcParent": "cron",
"Proc": "cron",
"ProcVersion": "3.0pl1-137",
"ProcUser": "root",
"ProcGroup": "root",
"ProcPPID": 990,
"ProcPID": 2122368,
"ProcTID": 2122368,
"ProcUID": 0,
"ProcGID": 0,
"ProcAge": 18.100170007,
"SockRole": "CLIENT",
"SockAddress": "/run/systemd/journal/dev-log",
"SockFamily": "AF_UNIX",
"SockTxBytes": 192,
"SockAge": 18.095146325,
"App": "SYSLOG",
"AppTxSyslog": [{
"Facility": "Security/Authorization",
"Severity": "Notice (5)",
"Priority": 85,
"Version": 0,
"Timestamp": "Sep 16 14:30:01",
"Appname": "CRON",
"ProcId": "2122368",
"Message": "pam_unix(cron:session): session opened for user root(uid=0) by (uid=0)"
},
{
"Facility": "Security/Authorization",
"Severity": "Informational (6)",
"Priority": 86,
"Version": 0,
"Timestamp": "Sep 16 14:30:01",
"Appname": "CRON",
"ProcId": "2122368",
"Message": "pam_unix(cron:session): session closed for user root"
}]
}
Kernel 5.10+ compiled with:
- CONFIG_BPF=y
- CONFIG_KPROBES=y
- CONFIG_KRETPROBES=y
- CONFIG_DEBUG_INFO_BTF=y
- Maps (since 4.1+) to perform filesystem event aggregation in hash tables
- Ringbuffer (since 5.8+) to share data between kernel eBPF program and user-space application
- Global variables (since 5.5) for parameterization of application behavior
- vmlinux.h file in binary form at /sys/kernel/btf/vmlinux
- Libraries libelf and libz installed
Kernel 5.10+ compiled with Just-In-Time eBPF compiler (JIT):
- CONFIG_BPF_JIT=y
JIT system control settings enabled:
- net.core.bpf_jit_enable=1
The following link provides an overview of Linux distributions with eBPF CO-RE & BTF enabled by default:
Linux Distributions w/ eBPF CO-RE & BTF
For high performance UDP output the following kernel network settings are recommended:
- sysctl -w net.core.rmem_max=134217728
- sysctl -w net.core.wmem_max=134217728
Usage:
kflowd [-m file,socket] [-t IDLE,ACTIVE] [-e EVENTS] [-o json|json-min|table] [-v] [-c]
[-p dns|http|syslog=PROTO/PORT,...] [-u IP:PORT] [-q] [-d] [-V] [-T TOKEN] [-P PATH]
[-D PROCESS], [-l] [--legend], [-h] [--help], [--version]
-m file,socket Monitor only specified kernel subsystem (filesystem or sockets)
(default: all, option omitted!)
-t IDLE,ACTIVE Timeout in seconds for idle or active network sockets until export
(default: idle '15' seconds, active '1800' seconds)
-e EVENTS Max number of filesystem events per aggregated record until export
(default: disabled, '1': no aggregation)
-o json Json output with formatting (default)
json-min Json output with minimal formatting
table Tabular output with limited keys and no UDP output
-v Version of executable files identified by installed package
(supported only for rpm- and deb-based package management)
-c Checksum hashes of MD5 and SHA256 calculated for executables
-p dns=PROTO/PORT,... Port(s) examined for decoding of DNS application protocol
(default: 'dns=udp/53,tcp/53', disabled: 'dns=off')
-p http=PROTO/PORT,... Port(s) examined for decoding of HTTP application protocol
(default: 'http=tcp/80', disabled: 'http=off')
-p syslog=PROTO/PORT,... Port(s) examined for decoding of SYSLOG application protocol
(default: 'syslog=udp/514,tcp/514,unix', disabled: 'syslog=off')
-u IP:PORT,... UDP server(s) IPv4 or IPv6 address to send json output to.
Output also printed to stdout console unless quiet option -q or
daemon mode -d specified
-q Quiet mode to suppress output to stdout console
-d Daemonize program to run in background
-V Verbose output
Print eBPF load and co-re messages on start of eBPF program
to stderr console
-T TOKEN Token specified on host to be included in json output
-P PATH Path to search for kflowd plugin modules (default: '../lib/')
-l, --legend Show legend
-h, --help Show help
--version Show version
-D PROCESS Debug
Print ebpf kernel log messages of process or expiration queue to
kernel trace pipe (any process: '*', with quotes!, queue: 'q')
Use command:
'sudo cat /sys/kernel/debug/tracing/trace_pipe'
Examples:
sudo ./kflowd # terminal mode
sudo ./kflowd -m file,socket -v -c -u 1.2.3.4:2056,127.0.0.1:2057 -d # daemon mode
sudo ./kflowd -m socket -v -c -u 1.2.3.4:2056 -V -D '*' # debug mode
sudo ./kflowd --legend # show legend
sudo ./kflowd --version # show version
- Kernel version 5.10+ compiled with BTF for CO-RE:
uname -a cat /boot/config-* | grep CONFIG_DEBUG_INFO_BTF - BPF enabled in file /etc/sysctl.conf:
... kernel.bpf_stats_enabled=1 kernel.unprivileged_bpf_disabled=0
-
Debian-based (Ubuntu, Mint)
- Install libraries:
sudo apt install libz-dev sudo apt install libelf-dev sudo apt install libcap-dev sudo apt install libbfd-dev sudo apt install libc6-dev-i386 - Install Clang 16+ toolchain:
sudo apt install build-essential sudo apt install pkg-config sudo apt install clang-16* sudo apt install llvm-16* sudo ln -s /usr/bin/clang-16 /usr/bin/clang sudo ln -s /usr/bin/llvm-strip-16 /usr/bin/llvm-strip - Install nfpm Linux packager:
echo 'deb [trusted=yes] https://repo.goreleaser.com/apt/ /' | sudo tee /etc/apt/sources.list.d/goreleaser.list sudo apt update sudo apt install nfpm
- Install libraries:
-
Redhat-based (Amazon Linux, Fedora)
- Install libraries:
sudo yum install zlib-devel sudo yum install elfutils-libelf-devel sudo yum install libcap-devel sudo yum install binutils-devel sudo yum install glibc-devel.i386 or .i686 - Install Clang 16+ toolchain:
sudo yum groupinstall 'Development Tools' sudo yum install pkgconfig sudo yum install clang* sudo yum install llvm* - Install nfpm Linux packager:
echo '[goreleaser] name=GoReleaser baseurl=https://repo.goreleaser.com/yum/ enabled=1 gpgcheck=0' | sudo tee /etc/yum.repos.d/goreleaser.repo sudo yum install nfpm
- Install libraries:
git clone https://github.com/tarsal-oss/kflowd.git
cd kflowd
git submodule update --init --recursive
cd src
make
make rpm deb
Packages can be installed on Linux x86_64 and arm64 based platforms:
- Debian
sudo apt install ./kflowd_x.x.x_amd64.deb
sudo apt install ./kflowd_x.x.x_arm64.deb
- Redhat
sudo yum install ./kflowd-x.x.x.x86_64.rpm
sudo yum install ./kflowd-x.x.x.aarch64.rpm
Note that build artifacts can be downloaded under GitHub Actions in the Artifacts section of the kflowd-ci workflow run with binaries and packages compatible for both x86_64 and arm64 platforms (glibc 2.31+):
Pre-built binaries, RPM and DEB packages (zipped)
This work is licensed under GNU General Public License v2.0.
SPDX-License-Identifier: GPL-2.0
- libbpf+CO-RE: Andrii Nakryiko's Blog, BPF CO-RE Reference Guide
- eBPF Tracing: Brendan Gregg, Linux Extended BPF (eBPF) Tracing Tools
- SHA256: Cgminer (Bitcoin mining project), Fast SHA256 Implementation
- MD5: RSA Data Security, MD5 Message-Digest Algorithm
