BGP Optimizer Causes Thousands Of Fake Routes
Earlier today many BGPmon users received one or more alerts informing them that their autonomous system (AS) started to announce a more-specific prefix. BGPmon classified many of these alerts as possible BGP man-in-the-middle (MITM) attacks. Here is an example alert:
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Possible BGP MITM attack (Code: 21)
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Your prefix: 23.20.0.0/15:
Prefix Description: acxiom-online.com --- Amazon EC2 IAD prefix
Update time: 2015-03-26 11:27 (UTC)
Detected by #peers: 24
Detected prefix: 23.21.112.0/20
Announced by: AS14618 (AMAZON-AES - Amazon.com, Inc.,US)
Upstream AS: AS3257 (TINET-BACKBONE Tinet SpA,DE)
ASpath: 4608 24130 7545 6939 40633 18978 3257 14618
The alert shows the user was monitoring 23.20.0.0/15, normally announced by Amazon, Inc. (AS14618). In this case however, the detected prefix was the more specific 23.21.112.0/20. The netblock owners would have verified their BGP announcements and quickly recognized they did not originate this more-specific prefix. Further analysis pointed to the suspicion that a bad actor was impersonating Amazon. BGPmon algorithms alerted to this as well, and–within moments of the initial change–marked these events as a possible BGP MITM attack.
One reason for this classification is the way BGPmon understands and interprets AS Continue reading