Originally posted on 01/29/2016:
Here are the choices at blockchain.info
Enable API Access
Check the following option to allow access to this wallet through the wallet API.
Block Tor IP addresses
Enable the following option to prevent ip addresses part of the Tor network from accessing your wallet.
IP Address Whitelist
The whitelist is a list of trusted IP Addresses that are allowed to access your wallet via the merchant APIs and bypass certain security restrictions. You will still be able to access your wallet from other ip addresses however the connecting device must be authorized by email.
Multiple ip addresses should be comma separated. Use % as a wildcard. For example 127.0.0.% to whitelist
Multiple IP addresses should be comma separated.
Restrict To Whitelisted IP Addresses Only
Enable this to restrict access to your wallet to only IP addresses listed in the whitelist. You will not be able to login or access any API's from any computers not on the specified network however the mobile apps will continue to function once paired.
2FA choices: SMS, Yubikey, Email, Google Authenticator.