Elastic medium stable eql

Potential Linux Ransomware Note Creation Detected

This rule identifies a sequence of a mass file encryption event in conjunction with the creation of a .txt file with a file name containing ransomware keywords executed by the same process in a 1 second timespan. Ransomware is a type of malware that encrypts a victim's files or systems and demands payment (usually in cryptocurrency) in exchange for the decryption key. One important indicator of a ransomware attack is the mass encryption of the file system, after which a new file extension is added to the file.

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Detection Logic

sequence by process.entity_id, host.id with maxspan=1s
  [file where host.os.type == "linux" and event.type == "change" and event.action == "rename" and file.extension : "?*"
   and process.executable : ("./*", "/tmp/*", "/var/tmp/*", "/dev/shm/*", "/var/run/*", "/boot/*") and
   file.path : (
     "/home/*/Downloads/*", "/home/*/Documents/*", "/root/*", "/bin/*", "/usr/bin/*", "/var/log/*", "/var/lib/log/*",
     "/var/backup/*", "/var/www/*") and
   not (
     process.name : (
       "dpkg", "yum", "dnf", "rpm", "dockerd", "go", "java", "pip*", "python*", "node", "containerd", "php", "p4d",
       "conda", "chrome", "imap", "cmake", "firefox", "semanage", "semodule", "ansible-galaxy", "fc-cache", "jammy", "git",
       "systemsettings", "vmis-launcher", "bundle", "kudu-tserver", "suldownloader", "rustup-init", "bun"
     ) or
     process.executable in ("./runc", "./usr/bin/qemu-aarch64")
   )
  ] with runs=25
  [file where host.os.type == "linux" and event.action == "creation" and
   file.name : ("*restore*", "*lock*", "*recovery*", "*read*", "*instruction*", "*how_to*", "*ransom*")
  ]

Field Validations

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