File Transfer Topics: The Administrator's Library

Moving files between systems, companies, and people is one of the oldest jobs in IT — and still one of the easiest to get subtly wrong. This library is our attempt to write the resource we wish every administrator had: plain-English, vendor-honest explanations of how file transfer actually works, written for working admins including those just starting out.

Every series below is a set of in-depth articles on one pillar of the subject. The material is evergreen: protocols and principles rather than product news, with real commands, worked examples, and the failure stories that teach faster than theory. Each article defines its terms as it goes — if you can map a network drive, you can follow along. Start anywhere; the articles cross-link where subjects meet.

Protocols & Fundamentals

The foundation group: how transfers work, the protocols you will actually meet — FTP and its modes, SFTP, FTPS, SCP, rsync, HTTP, WebDAV, TFTP, AS2 — and the judgment to choose among them.

• File Transfer Fundamentals
  The core concepts every protocol shares: connections, push vs pull, transfer vs sync, integrity, and reliability.
• The FTP Protocol, Understood Properly
  The grand old protocol taken apart properly — channels, commands, reply codes, account models, and failure modes.
• Active vs Passive FTP
  The two modes demystified: who opens what, why firewalls care, and how to configure and troubleshoot both.
• SFTP In Depth
  SSH-based transfer in depth: architecture, keys, server lockdown, performance, and safe automation.
• FTPS In Depth
  FTP wrapped in TLS: explicit vs implicit, certificates, firewall behavior, and hardening.
• SFTP vs FTPS vs FTP: Choosing the Right Protocol
  The honest comparison and decision framework — including migration paths off plain FTP.
• SCP and SSH-Based Copying
  The quick-copy workhorse: mechanics, limits, command mastery, and bastion-host patterns.
• rsync and Delta Transfer
  Delta transfer explained and tamed: the algorithm, the flags that bite, and mirror/backup patterns.
• HTTP and HTTPS File Transfer
  The web as a transfer tool: uploads, curl patterns, presigned URLs, and large-file strategies.
• WebDAV
  Remote files over HTTP: what DAV adds, mounting drives, security, and where it still fits.
• Network Shares vs File Transfer
  Mapped drives vs transfer flows: semantics, WAN reality, SMB/NFS fundamentals, and hardening.
• TFTP
  The tiny bootstrap protocol: device configs, firmware, PXE boot, and containment.
• B2B Exchange Protocols: AS2 and EDI-Style Transfer
  Business-grade exchange: AS2 signing and receipts, EDI survival vocabulary, and partner onboarding.
• UDP-Accelerated Transfer for Distance and Scale
  When distance beats TCP: the bandwidth-delay product, acceleration explained, and free tuning first.
• Email Attachments as File Transfer
  The transfer system everyone uses anyway: limits, scanners, policy, and alternatives that stick.

Security

The protection group: thinking like an attacker, encryption on the wire and at rest, keys and certificates, hardened servers and edge architecture, scanning and egress control, evidence-grade logging, and zero trust translated into practice.

• File Transfer Threat Modeling
  Think like an attacker: motives, attack surface, the attacks transfer services actually see, and a practical risk assessment.
• Encryption in Transit
  TLS and SSH in plain words: what they protect, what they don't, finding cleartext, and cipher policy without a cryptography degree.
• Encryption at Rest and End-to-End with PGP
  Sealing the file itself: how PGP works, partner key management, encrypt-before-send automation, and at-rest protection.
• SSH Key Management for File Transfers
  Keys through their whole life: generate, store, distribute, rotate, inventory, and retire.
• Certificate Management for Transfer Endpoints
  Certificates without the outage: chains, CAs, installation, expiry monitoring, and mutual TLS.
• Authentication on Transfer Endpoints
  The front door done right: methods compared, service-account hygiene, MFA's honest place, and lockout design.
• Hardening Transfer Servers
  A layered hardening program: OS baseline, jails, information leakage, patching, and verification that it holds.
• DMZ and Gateway Architecture for File Exchange
  Placing exchange at the edge: DMZ patterns, keeping data out of the buffer zone, flow direction, and budget options.
• Retiring Plain FTP
  The retirement program: the business case, discovery, sequencing, partner communications, legacy containment, and proof.
• Anonymous and Guest Access
  The forgotten open doors: auditing for anonymous access, the few legitimate uses, lockdown, and modern alternatives.
• Brute-Force Protection and Access Restriction
  Ending credential attacks: lockouts, allowlisting, log-driven banning, key-only auth, and monitoring.
• Malware Scanning in File Flows
  Scanning where transfers actually flow: pipeline placement, quarantine design, scanner blind spots, and incident response.
• Data Loss Prevention for Transfers
  Knowing what leaves: the egress census, pattern controls, policy before tooling, and DLP effects on a budget.
• Permissions and Least Privilege on File Servers
  The control you already own: permission models, isolating directory design, least privilege, audits, and blast radius.
• Transfer Logging and Audit Trails
  Logs that answer questions: what to record, reading sessions, centralizing, tamper resistance, alerts, and audit reports.
• File Integrity Verification
  Proving the bytes arrived intact: hashing, end-to-end checks, manifests, corruption sources, and fail-closed automation.
• Digital Signatures, Non-Repudiation, and Proof of Delivery
  Proving who sent what: signatures in practice, non-repudiation, delivery receipts, timestamps, and evidence packs.
• Zero Trust Applied to File Movement
  The principles without the buzzwords: identity-centric access, segmentation, removing implicit trust, and a small-team roadmap.