picosnitch 0.11.4

Protect your privacy, see which applications make network connections

picosnitch

• Receive notifications whenever a new program connects to the network, or when it's modified
• Monitors your bandwidth, breaking down traffic by executable, hash, parent, domain, port, or user over time
• Can optionally check hashes or executables using VirusTotal
• Executable hashes are cached based on device + inode for improved performance, and works with applications running inside containers
• Uses BPF for accurate, low overhead bandwidth monitoring and fanotify to watch executables for modification
• Since applications can call others to send/receive data for them, the parent executable and hash is also logged for each connection
• Inspired by programs such as GlassWire, Little Snitch, and OpenSnitch

installation

AUR for Arch and derivatives

• install picosnitch manually or using your preferred AUR helper

PPA for Ubuntu and derivatives

• sudo add-apt-repository ppa:elesiuta/picosnitch
• sudo apt update
• sudo apt install picosnitch
• extra dependencies for dash (optional): dash, pandas, and plotly
• if you encounter issues, try a newer version of BCC (unofficial PPA)

PyPI for any Linux distribution with Python >= 3.8

• install the BPF Compiler Collection python package for your distribution
  • it should be called python-bcc or python-bpfcc
• install picosnitch using pip
  • pip3 install "picosnitch[full]" --upgrade --user
• create a service file for systemd to run picosnitch (recommended)
  • picosnitch systemd
• optional dependencies (will install from PyPI with [full] if not already installed)
  • for dash: dash, pandas, and plotly
  • for notifications: dbus-python, python-dbus, or python3-dbus (name depends on your distro and should be installed from their repo)
  • for sql server: one of psycopg, pymysql, mariadb, or psycopg2 (latter two not included with [full])
  • for VirusTotal: requests

usage

• running picosnitch
  • enable/disable autostart on reboot with systemctl enable|disable picosnitch
  • start/stop/restart with systemctl start|stop|restart picosnitch
  • or if you don't use systemd picosnitch start|stop|restart
• web user interface for browsing past connections
  • start with picosnitch dash
  • visit http://localhost:5100
• terminal user interface for browsing past connections
  • start with picosnitch view
  • space/enter: filter on entry backspace: remove filter h/H: cycle through history t/T: cycle time range u/U: cycle byte units r: refresh view q: quit
• show usage with picosnitch help

configuration

• config is stored in ~/.config/picosnitch/config.json
  • restart picosnitch if it is currently running for any changes to take effect

{
  "Bandwidth monitor": true, # Log traffic per connection since last db write
  "DB retention (days)": 365, # How many days to keep connection logs in snitch.db
  "DB sql log": true, # Write connection logs to snitch.db (SQLite)
  "DB sql server": {}, # Write connection logs to a MariaDB, MySQL, or PostgreSQL server
  "DB text log": false, # Write connection logs to conn.log
  "DB write limit (seconds)": 10, # Minimum time between writing connection logs
  # increasing it decreases disk writes by grouping connections into larger time windows
  # reducing time precision, decreasing database size, and increasing hash latency
  "Desktop notifications": true, # Try connecting to dbus to show notifications
  "Every exe (not just conns)": false, # Check every running executable with picosnitch
  # these are treated as "connections" with a port of -1
  # this feature is experimental but should work fairly well, errors should be expected as
  # picosnitch is unable to open file descriptors for some extremely short-lived processes
  # if you just want logs (no hashes) to trace process hierarchy, see execsnoop or forkstat
  "Log addresses": true, # Log remote addresses for each connection
  "Log commands": true, # Log command line args for each executable
  "Log ignore": [], # List of hashes (str), domains (str), or ports (int)
  # will omit connections that match any of these from the connection log
  # domains will match any that start with the provided string, hashes or ports are exact
  # the process name, executable, and hash will still be recorded in record.json
  # use with caution since applications could still be compromised without affecting hash
  # e.g. via shared libraries, loading scripts, extensions, etc.
  "Perf ring buffer (pages)": 64, # Power of two number of pages for BPF program
  # only change this if it is giving you errors
  "Set RLIMIT_NOFILE": null, # Set the maximum number of open file descriptors (int)
  # it is used for caching process executables and hashes (typical system default is 1024)
  # this is good enough for most people since caching is based on executable device + inode
  # fanotify is used to detect if a cached executable is modified to trigger a hash update
  "VT API key": "", # API key for VirusTotal, leave blank to disable (str)
  "VT file upload": false, # Upload file if hash not found, only hashes are used by default
  "VT request limit (seconds)": 15 # Number of seconds between requests (free tier quota)
}

logging

• a log of seen executables is stored in ~/.config/picosnitch/exe.log
  • this is a history of your notifications
• a record of seen executables is stored in ~/.config/picosnitch/record.json
  • this is used for determining whether to create a notification
  • it contains known process name(s) by executable, executable(s) by process name, and sha256 hash(es) with VirusTotal results by executable
• enable DB sql log (default) to write the full connection log to ~/.config/picosnitch/snitch.db
  • this is used for picosnitch dash, picosnitch view, or something like DB Browser
  • note, connection times are based on when the group is processed, so they are accurate to within DB write limit (seconds) at best, and could be delayed if the previous group is slow to hash
  • notifications are handled by a separate subprocess, so they are not subject to the same delays as the connection log
• use DB sql server to write the full connection log to a MariaDB, MySQL, or PostgreSQL server
  • this is independent of DB sql log and is used for providing an off-system copy to prevent tampering (use GRANT to assign privileges)
  • to configure, add the key client to DB sql server with value mariadb, psycopg, psycopg2, or pymysql, you can also optionally set table_name
  • assign remaining connection parameters for mariadb, psycopg, or pymysql to DB sql server as key/value pairs
• enable DB text log to write the full connection log to ~/.config/picosnitch/conn.log
  • this may be useful for watching with another program
  • it contains the following fields, separated by commas (commas, newlines, and null characters are removed from values)
  • executable,name,cmdline,sha256,time,domain,ip,port,uid,parent_exe,parent_name,parent_cmdline,parent_sha256,conns,sent,received
• the error log is stored in ~/.config/picosnitch/error.log
  • errors will also trigger a notification and are usually caused by far too many or extremely short-lived processes/connections, or suspending your system while a new executable is being hashed
  • while it is very unlikely for processes/connections to be missed (unless Every exe (not just conns) is enabled), picosnitch was designed such that it should still detect this and log an error giving you some indication of what happened
  • for most people in most cases, this should raise suspicion that a program may be misbehaving
  • a program should not be able to hide from picosnitch (either by omission or spoofing another program) without picosnitch reporting an error
  • see limitations below for other sources of errors

limitations

• while picosnitch aims to be as reliable as possible, there are some fundamental limitations for these types of tools which you should be aware of in order to decide if this approach suits your purpose, and how to use it effectively
• detecting open sockets, monitoring traffic, and identifying the process should be fairly reliable with BPF, however accurately identifying the application behind it can be difficult, especially if has malicious intent
• the process name is trivial to change, the path can be set to anything with mount namespaces, including impersonating an already existing executable (or replacing it), and cmdline arguments can be faked by calling itself or a script with bogus arguments
• hashing the executable can help with this, however it is an imperfect solution since only the process executable itself is hashed and there are still ways a program can hide
  • applications could also be compromised via shared libraries, loading scripts, extensions, etc., this could be improved by supplementing with other host-based intrusion detection systems (HIDS) such as AIDE or something like debsums (with caveats)
  • applications such as AppImages which use FUSE may not be readable as root, preventing the executable from being hashed, you may want to avoid them in order to reduce log noise that malicious programs could use to hide
  • if a process is too short lived, picosnitch may not be able to open a file descriptor in time in order to hash it
  • the device and inode of the opened file descriptor is checked against what was reported by the BPF program to detect if the executable was replaced, however BTRFS uses non-unique inodes, negating this protection
• if for any reason the executable fails to hash, the traffic will still be logged with whatever information was available and you will be notified of an error
• too many processes or connections could cause the connection data to be lost if callbacks are not processed fast enough, this will be detected, logging the error and triggering a notification
• depending on your level of concern for privacy/security, you may want to keep an off-system copy of your logs to protect them
• instead of playing cat and mouse by trying to cover these edge cases, and any other method a malicious program can use to hide, the focus is on doing what it can do, and do it well, and that is accurately monitoring traffic, and it is up to you to decide whether it looks abnormal, whether it's the amount, time, destination for a specific executable
• for these reasons (and probably others), if you want a more secure method to isolate or deny traffic per application, you need to sandbox them with something such as firejail, flatpak, or a virtual machine

building from source

• install dependencies listed under installation
• install python-setuptools
• install picosnitch with python setup.py install --user
• see other options with python setup.py [build|install] --help
• you can also run the script picosnitch.py directly