Detect File Transfer Protocols in Sumo Logic CSE
Adversaries may communicate using application layer protocols associated with transferring files to avoid detection/network filtering by blending in with existing traffic. Commands to the remote system, and often the results of those commands, will be embedded within the protocol traffic between the client and server. Protocols such as SMB, FTP, FTPS, and TFTP that transfer files may be very common in environments. Packets produced from these protocols may have many fields and headers in which data can be concealed. Data could also be concealed within the transferred files. An adversary may abuse these protocols to communicate with systems under their control within a victim network while also mimicking normal, expected traffic.
MITRE ATT&CK
- Tactic
- Command and Control
- Technique
- T1071 Application Layer Protocol
- Sub-technique
- T1071.002 File Transfer Protocols
- Canonical reference
- https://attack.mitre.org/techniques/T1071/002/
Sumo Detection Query
(_sourceCategory=network/firewall OR _sourceCategory=network/paloalto OR _sourceCategory=network/cisco/asa OR _sourceCategory=network/fortinet)
| where dest_port in ("20","21","69","139","445","990")
| where action in ("allow","allowed","permit","accept","built")
| where !isPrivateIP(dest_ip)
| where dest_ip != "0.0.0.0"
| eval Protocol = if(dest_port in ("20","21","990"), "FTP/FTPS",
if(dest_port in ("445","139"), "SMB",
if(dest_port == "69", "TFTP", "Unknown")))
| eval BytesSent = toLong(if(isNull(bytes_out), "0", bytes_out))
| eval BytesReceived = toLong(if(isNull(bytes_in), "0", bytes_in))
| stats
count as ConnectionCount,
sum(BytesSent) as TotalBytesSent,
sum(BytesReceived) as TotalBytesReceived,
min(_messageTime) as FirstSeen,
max(_messageTime) as LastSeen,
values(user) as Users
by src_ip, dest_ip, dest_port, Protocol, process_name
| where ConnectionCount > 3
| eval ExfilRisk = if(TotalBytesSent > 10485760, "HIGH",
if(TotalBytesSent > 1048576, "MEDIUM", "LOW"))
| formatDate(toLong(FirstSeen), "yyyy-MM-dd HH:mm:ss") as FirstSeen
| formatDate(toLong(LastSeen), "yyyy-MM-dd HH:mm:ss") as LastSeen
| fields LastSeen, FirstSeen, src_ip, dest_ip, dest_port, Protocol, process_name, Users, ConnectionCount, TotalBytesSent, TotalBytesReceived, ExfilRisk
| sort by ConnectionCount descSumo Logic query against network firewall source categories to detect hosts that successfully connect to external IPs on file transfer protocol ports (FTP 20/21/990, SMB 445/139, TFTP 69) more than 3 times within the search window. Aggregates per source IP, destination, and protocol; computes byte volumes and assigns exfiltration risk tier. Compatible with Palo Alto, Cisco ASA, and Fortinet log formats ingested under standard Sumo Logic source categories.
Data Sources
Required Tables
False Positives & Tuning
- Legitimate FTP-based website publishing tools (e.g., FileZilla in automated mode, WinSCP scripted transfers) used by web developers or marketing teams deploying content to external hosting providers.
- Enterprise DLP or backup agents that transfer data over FTP/FTPS to vendor-managed cloud storage, generating large sustained BytesSent volumes from a known service account.
- Security scanners or asset inventory tools that probe external partner IPs on SMB port 445 as part of scheduled vulnerability assessments, producing bursts of allowed connections.
Other platforms for T1071.002
Testing Methodology
Validate this detection against 3 adversary techniques from Atomic Red Team. Each test below lists the behaviour to exercise and the telemetry you should expect to see. Executable commands and cleanup steps are available with Pro.
- Test 1FTP C2 Simulation via Built-in Client
Expected signal: Sysmon Event ID 1: Process creation for ftp.exe with -s: flag pointing to script file. Sysmon Event ID 3: Network connection attempt to 127.0.0.1:21. Sysmon Event ID 11: File creation of ftp_c2.txt in TEMP directory.
- Test 2SMB Named Pipe C2 Simulation
Expected signal: Sysmon Event ID 17: Pipe Created with PipeName=\\msagent_f1. Sysmon Event ID 1: PowerShell process creation with named pipe creation in command line. The pipe name 'msagent_f1' is a known Cobalt Strike default pipe name pattern.
- Test 3FTP Data Exfiltration via curl
Expected signal: Sysmon for Linux Event ID 3: Network connection from curl to 127.0.0.1:21. Process creation event for curl with -T (upload) flag and ftp:// URL. File creation event for the test file.
References (6)
- https://attack.mitre.org/techniques/T1071/002/
- https://www.us-cert.gov/ncas/alerts/TA18-074A
- https://www.welivesecurity.com/wp-content/uploads/2019/08/ESET_Machete.pdf
- https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1071.002/T1071.002.md
- https://thedfirreport.com/2021/08/29/cobalt-strike-a-defenders-guide/
- https://www.mandiant.com/resources/blog/apt41-dual-espionage-and-cyber-crime-operation
Unlock Pro Content
Get the full detection package for T1071.002 including response playbook, investigation guide, and atomic red team tests.