Approximately how many packets are usually required to conduct a successful FMS attack onWEP?

250,000 packets significantly overestimates the number required - the FMS attack is efficient enough through IV-based statistical analysis to succeed with far fewer captured frames.

The FMS (Fluhrer, Mantin, Shamir) attack exploits weaknesses in WEP's RC4 key scheduling algorithm by targeting packets with weak Initialization Vectors. Approximately 20,000 packets containing exploitable weak IVs are typically required to accumulate enough statistical correlations to recover the WEP key bytes through this cryptanalysis method.

10,000,000 packets is an extreme overestimate; the FMS attack targets specific weak IV patterns and does not require that volume of generic captured traffic.

A single packet with a weak IV is statistically insufficient - the FMS attack must aggregate correlations across many weak IV samples to recover each key byte with sufficient confidence.