As a Jailbreaker or hacker you may, from time to time, need a version of IOS which is no longer the current firmware for your device.
Below are links direct to the Apple download service for all available versions of IOS for the various iPhone models right back to the original!
Use these links whenever you want to be assured of getting a legitimate official stock firmware.
iPhone4S
5.0.1 (9A406) http://appldnld.apple.com/iPhone4/04...6_Restore.ipsw
5.0.1 (9A405) http://appldnld.apple.com/iPhone4/04...5_Restore.ipsw
5.0 http://appldnld.apple.com/iPhone4/04...4_Restore.ipsw
iPhone4 GSM
5.0.1 http://appldnld.apple.com/iPhone4/04...5_Restore.ipsw
5.0 http://appldnld.apple.com/iPhone4/04...4_Restore.ipsw
4.3.5 http://appldnld.apple.com/iPhone4/04...1_Restore.ipsw
4.3.4 http://appldnld.apple.com/iPhone4/04...2_Restore.ipsw
4.3.3 http://appldnld.apple.com/iPhone4/04...2_Restore.ipsw
4.3.2 http://appldnld.apple.com/iPhone4/04...7_Restore.ipsw
4.3.1 http://appldnld.apple.com/iPhone4/04...4_Restore.ipsw
4.3 http://appldnld.apple.com/iPhone4/04...0_Restore.ipsw
4.2.1 http://appldnld.apple.com/iPhone4/06...8_Restore.ipsw
4.1 http://appldnld.apple.com/iPhone4/06...7_Restore.ipsw
4.0.2 http://appldnld.apple.com/iPhone4/06...0_Restore.ipsw
4.0.1 http://appldnld.apple.com/iPhone4/06...6_Restore.ipsw
4.0 http://appldnld.apple.com.edgesuite....3_Restore.ipsw
iPhone4 CDMA
5.0.1 http://appldnld.apple.com/iPhone4/04...5_Restore.ipsw
5.0 http://appldnld.apple.com/iPhone4/04...4_Restore.ipsw
4.2.10 http://appldnld.apple.com/iPhone4/04...0_Restore.ipsw
4.2.9 http://appldnld.apple.com/iPhone4/04...1_Restore.ipsw
4.2.8 http://appldnld.apple.com/iPhone4/04...1_Restore.ipsw
4.2.7 http://appldnld.apple.com/iPhone4/04...3_Restore.ipsw
4.2.6 http://appldnld.apple.com/iPhone4/04...0_Restore.ipsw
iPhone3GS
5.0.1 http://appldnld.apple.com/iPhone4/04...5_Restore.ipsw
5.0 http://appldnld.apple.com/iPhone4/04...4_Restore.ipsw
4.3.5 http://appldnld.apple.com/iPhone4/04...1_Restore.ipsw
4.3.4 http://appldnld.apple.com/iPhone4/04...2_Restore.ipsw
4.3.3 http://appldnld.apple.com/iPhone4/04...2_Restore.ipsw
4.3.2 http://appldnld.apple.com/iPhone4/04...7_Restore.ipsw
4.3.1 http://appldnld.apple.com/iPhone4/04...4_Restore.ipsw
4.3 http://appldnld.apple.com/iPhone4/04...0_Restore.ipsw
4.2.1 http://appldnld.apple.com/iPhone4/06...a_Restore.ipsw
4.1 http://appldnld.apple.com/iPhone4/06...7_Restore.ipsw
4.0.2 http://appldnld.apple.com/iPhone4/06...0_Restore.ipsw
4.0.1 http://appldnld.apple.com/iPhone4/06...6_Restore.ipsw
4.0 http://appldnld.apple.com.edgesuite....3_Restore.ipsw
3.1.3 http://appldnld.apple.com.edgesuite....8_Restore.ipsw
3.1.2 http://appldnld.apple.com.edgesuite....1_Restore.ipsw
3.1 http://appldnld.apple.com.edgesuite....4_Restore.ipsw
3.0.1 http://appldnld.apple.com.edgesuite....0_Restore.ipsw
3.0 http://appldnld.apple.com.edgesuite....1_Restore.ipsw
iPhone3G
4.2.1 http://appldnld.apple.com/iPhone4/06...8_Restore.ipsw
4.1 http://appldnld.apple.com/iPhone4/06...7_Restore.ipsw
4.0.2 http://appldnld.apple.com/iPhone4/06...0_Restore.ipsw
4.0.1 http://appldnld.apple.com/iPhone4/06...6_Restore.ipsw
4.0 http://appldnld.apple.com.edgesuite....3_Restore.ipsw
3.1.3 http://appldnld.apple.com.edgesuite....8_Restore.ipsw
3.1.2 http://appldnld.apple.com.edgesuite....1_Restore.ipsw
3.1 http://appldnld.apple.com.edgesuite....4_Restore.ipsw
3.0.1 http://appldnld.apple.com.edgesuite....0_Restore.ipsw
3.0 http://appldnld.apple.com.edgesuite....1_Restore.ipsw
2.2.1 http://appldnld.apple.com.edgesuite....1_Restore.ipsw
2.2 http://appldnld.apple.com.edgesuite....7_Restore.ipsw
2.1 http://appldnld.apple.com.edgesuite....6_Restore.ipsw
2.0.2 http://appldnld.apple.com.edgesuite....1_Restore.ipsw
2.0.1 http://appldnld.apple.com.edgesuite....8_Restore.ipsw
2.0 http://appldnld.apple.com.edgesuite....7_Restore.ipsw
iPhone (Original)
3.1.3 http://appldnld.apple.com.edgesuite....8_Restore.ipsw
3.1.2 http://appldnld.apple.com.edgesuite....1_Restore.ipsw
3.1 http://appldnld.apple.com.edgesuite....4_Restore.ipsw
3.0.1 http://appldnld.apple.com.edgesuite....0_Restore.ipsw
3.0 http://appldnld.apple.com.edgesuite....1_Restore.ipsw
2.2.1 http://appldnld.apple.com.edgesuite....1_Restore.ipsw
2.2 http://appldnld.apple.com.edgesuite....7_Restore.ipsw
2.1 http://appldnld.apple.com.edgesuite....6_Restore.ipsw
2.0.2 http://appldnld.apple.com.edgesuite....1_Restore.ipsw
2.0.1 http://appldnld.apple.com.edgesuite....8_Restore.ipsw
2.0 http://appldnld.apple.com.edgesuite....7_Restore.ipsw
1.1.4 http://appldnld.apple.com.edgesuite....2_Restore.ipsw
1.1.3 http://appldnld.apple.com.edgesuite....3_Restore.ipsw
1.1.2 http://appldnld.apple.com.edgesuite....b_Restore.ipsw
1.1.1 http://appldnld.apple.com.edgesuite....a_Restore.ipsw
1.0.2 http://appldnld.apple.com.edgesuite....8_Restore.ipsw
1.0.1 http://appldnld.apple.com.edgesuite....5_Restore.ipsw
1.0.0 http://appldnld.apple.com.edgesuite....a_Restore.ipsw