Abstract: An automated security assessment service of a service provider network may identify, and notify a customer of, misconfigured VM instances that can be access (e.g., via the Internet). A scanner tool may call an automated reasoning service to identify any VM instances of a customer that can be accessed, and may receive information from the automated reasoning service that is usable to exchange packets with those identified instances. The scanner tool can use the information to send requests to the identified instances. After receiving responses from the identified instances, the scanner tool can store, in storage of a network-based storage service, and in association with a customer account of the customer, encrypted data about the results of the scan (e.g., any VM instances that are vulnerable to attackers), and this encrypted data is thereby accessible to the customer with proper decrypt permissions.

Abstract: A network change verification (NCV) system is disclosed for checking whether a proposed configuration change on a network alters the way that the network controls recently observed network flows. In embodiments, the system builds an observed flow control model (OFCM) from logs of recent flows observed in the network. The OFCM, which may be periodically updated based on newly observed flows, provides a compact representation of how individual network flows were ostensibly controlled by the network. When a proposed configuration change is received, the system analyzes the change against the OFCM to check whether the change will alter how the network controls recently observed flows. If so, the proposed change is blocked, and an alert is generated identifying flows that are affected by the change. The NCV system thus prevents network operators from accidentally making changes on the network that will materially alter the behavior of the network.

Abstract: Features are disclosed for managing routing rules stored by a routing device and used to manage network traffic in a network. A computing device can receive multiple routing rules corresponding to multiple routing devices in the network. The computing device can use a formal specification and a snapshot to generate a model of the network. The computing device may use the model in order to statically determine the set of possible paths without causing the transmission of data between a routing device and a destination. the computing device may compare the identified routing rules and the possible paths in order to determine excess routing rules. The computing device may remove the excess routing rules from the routing rules for each routing device such that each routing device routes subsequent network traffic based on the updated routing rules.

Abstract: This disclosure describes techniques for identifying blocked paths and network configuration settings that block paths in networks, such as network paths in a virtual private cloud (VPC). The configuration of virtual networks depends on the correct configuration of many networking resources, such as firewalls, security groups, routing lists, access control lists (ACLs), and the like. In some cases, an analysis that uses formal methods can be performed to determine a network configuration of a virtual network. Using the network configuration information, network paths that are blocked and network configuration settings that may be blocking one or more of the network paths can be determined. The PAS can provide an explanation of what is blocking the network paths. For example, the PAS may identify that a configuration setting of a firewall, router, network gateway, an access control list (ACL), and the like may be blocking a network path.