The four groups
C standard library functions
STRCPY · MEMCPY · MALLOC · PRINTF
Notoriously-unsafe C string APIs
GETS · STRCAT · SPRINTF · SCANF
All four can write past the destination buffer if you don't guard them.
Memory-corruption mitigations
ASLR · DEP · STACK CANARY · FORTIFY
Words paired with OVERFLOW
STACK · INTEGER · ARITHMETIC · TWITTER
Stack overflow, integer overflow, arithmetic overflow, Twitter Overflow (the site that came before Stack Exchange? No — just the cheeky joke).
Why this puzzle works
The unsafe-C-strings group (green) shares DNA with the C-stdlib group (yellow): PRINTF and SPRINTF are siblings, but one is in 'used everywhere' and the other in 'don't use, ever'. STRCAT also unsafe; the safe alternative would be strncat. STACK CANARY is a four-syllable tile that scares off some players — but it's a single concept (the 'canary' value placed between local variables and the return address).
How to read a Connectle without solving it
A code-themed grouping puzzle rewards counting as much as recognition. Start by listing every plausible group, then notice which tiles appear in two lists. Whichever group has exactly four unambiguous members is your anchor — solve it first and the rest of the board collapses by elimination. The hardest tier (purple) is almost always wordplay: tiles that share a prefix or suffix, not a concept. If a tile feels orphaned, ask whether the same word could follow or precede a common engineering word like root, stack, cache, or queue.