Undetected rhymes with:
unprotected, defected, deflected, dejected, disaffected, disconnected, disrespected, ejected, inspected, interconnected, interjected, intersected, misdirected, recollected, reconnected, redirected, rejected, respected, resurrected, subjected, unaffected, uncollected, unconnected, uncorrected, unelected, unexpected, uninfected, unprotected, unsuspected
Undetected sounds like:
unadjust, unadjusted, unattached, undecided, undisguised, uneducated, unhedged, unindicted, unmatched, unmitigated, unnoticed, untaxed, untested, untouched