CompTIA Exam Prep - ITF+, A+, Network+, Security+, CySA+

Trivial File Transfer Protocol is deliberately minimal: no authentication, no encryption, no directory listing, no way to delete or rename. It runs on UDP port 69 and does two things — read a file, write a file. That minimalism is why it is still deployed decades after it should have disappeared, and also why it is a liability wherever it is reachable. How it works A client sends a read or write request to UDP 69. The server responds from a different , ephemeral port, and the rest of the transfer continues between the client's port and that one. This surprises people configuring firewalls: opening UDP 69 alone is not enough, and stateful inspection or a protocol helper is needed for the transfer to complete. Data moves in fixed-size blocks, traditionally 512 bytes, each acknowledged before the next is sent. That lockstep behavior makes it simple to implement and slow over links with any latency. A block smaller than the full size signals the end of the file. Because UDP provi...

SMTP — Simple Mail Transfer Protocol — is how email gets sent . That word matters, because the most common exam trap on this topic is confusing sending with retrieving. SMTP pushes mail out. POP3 and IMAP pull mail down. One protocol for sending, two for receiving. When you click Send, your client hands the message to a mail server over SMTP. That server finds the recipient's mail server and relays it there, again over SMTP. The message then sits in the recipient's mailbox until their client collects it — and that collection uses POP3 or IMAP, never SMTP. The Ports Port Use Encryption 25 Server-to-server relay Opportunistic STARTTLS, historically none 587 Client submission — the modern standard STARTTLS, authentication required 465 Client submission, implicit TLS SMTPS — encrypted from the first byte 2525 Unofficial alternative Varies — used when 25 is blocked The distinction between 25 and 587 is worth understanding rather than memorizing. Port 25 is for ser...

IMAP — Internet Message Access Protocol — retrieves email from a mail server while leaving it there, keeping every device you own in sync. It is the protocol behind the fact that reading a message on your phone marks it read on your laptop. IMAP synchronizes. POP3 downloads. That one sentence answers most exam questions on this topic. And remember the direction: SMTP sends mail; IMAP and POP3 retrieve it. Confusing sending with receiving is the other common error. IMAP Versus POP3   IMAP POP3 Where mail lives On the server Downloaded to the client Multiple devices Fully synchronized Poorly — each device gets its own copy Folders Server-side, synchronized Local only; inbox only on the server Read/unread and flags Synchronized across devices Local to each client Server storage used High Low — mail is typically deleted after download Offline access Cached copies Full, by design Default port 143 110 Secure port 993 (IMAPS) 995 (POP3S) Those four port number s — ...

DNS record types are pure recall, and they turn up on Network+, Security+, and A+ alike. The list is short enough to own in an evening, and several of them carry security implications that exams test separately. A record maps a name to an IPv4 address. Almost everything else is a variation on that idea — different address family, different purpose, or a pointer to another name. The Records You Must Know Record Maps Notes A Hostname → IPv4 address The fundamental record. "Address record." AAAA Hostname → IPv6 address Called a "quad-A" record. Four As because IPv6 addresses are four times the size of IPv4. CNAME Alias → another hostname Canonical name. Points a name at another name , never at an IP address. MX Domain → mail server Mail exchanger. Carries a priority value; lower numbers are preferred. NS Domain → authoritative name server Delegates a zone to the servers responsible for it. PTR IP address → hostname Pointer. The reverse of an A record, used...