Find minimum time for irrecoverable password

A password is a string s of length n. A virus attacks positions in a 1-indexed order given by a permutation attackOrder[1..n]. At second t (1 <= t <= n), the character at position attackOrder[t] is replaced by a malicious character ''. The password is irrecoverable once the number of substrings containing at least one '' is >= m. Find the minimum time t after which the password becomes irrecoverable; if it is irrecoverable at the start, return 1. Implement findMinimumTime(password, attackOrder, m) and state the algorithm and its time and space complexity.