Abstract: Methods, apparatus and computer software products implement embodiments of the present invention that include protecting a computer system, by collecting information from data traffic transmitted between multiple local nodes on a private data network and public IP addresses corresponding to multiple remote nodes on a public data network. DNS resolutions are detected in the collected information, each DNS resolution identifying a local node requesting the resolution with respect to a URI and a public IP address corresponding to the URI. Transmissions from the local nodes to the public IP addresses are detected in the collected information at respective times, and the detected DNS resolutions are compared to the detected transmissions so as to identify the transmissions from the local nodes to the public IP addresses that were not resolved by the DNS resolutions. Finally, a protective action is initiated with respect to at least some of the identified transmissions.

Abstract: Methods, apparatus and computer software products implement embodiments of the present invention that include protecting a computer system, by collecting information from data traffic transmitted between multiple local nodes on a private data network and public IP addresses corresponding to multiple remote nodes on a public data network. DNS resolutions are detected in the collected information, each DNS resolution identifying a local node requesting the resolution with respect to a URI and a public IP address corresponding to the URI. Transmissions from the local nodes to the public IP addresses are detected in the collected information at respective times, and the detected DNS resolutions are compared to the detected transmissions so as to identify the transmissions from the local notes to the public IP addresses that were not resolved by the DNS resolutions. Finally, a protective action is initiated with respect to at least some of the identified transmissions.

Abstract: A method, including identifying, in network data traffic, a set of pairs of source and destination nodes, each pair having a given source node, a given destination node, and one or more ports accessed in the traffic between the nodes in each pair, and computing, for each pair, a respective baseline that indicates a first number of the ports that source nodes other than the given source node in the pair accessed on the given destination node during a first period. For each pair, a respective test score is computed that indicates a difference between a second number of the ports that the given source node in the pair accessed on the given destination node during a second period and the baseline, and a preventive action is initiated with respect to the given source node in any of the pairs for which the test score is greater than a threshold.

Abstract: A method, including identifying, in network traffic during multiple periods, scans, each scan including an access of multiple ports on a given destination node by a given source node, and computing, for each given source in the scans, an average of destinations whose ports were accessed by the given source during any scan by the given source, and a fraction of periods when the given source accessed at least one of the destinations in at least one scan performed by the given source node. A whitelist is assembled sources for which one or more of the following conditions applies: the average of destinations accessed in the scans was greater than a first threshold, and the fraction of periods during which at least one destination was accessed in at least one scan was greater than a second threshold. Upon detecting a scan by any non-whitelisted node, a preventive action is initiated.

Abstract: A method, including identifying, in network data traffic, multiple scans, each of the scans including an access, in the traffic, of multiple ports on a given destination node by a given source node during a time period. A group of high-traffic ports are identified in the traffic that include one or more ports that receive respective volumes of the traffic that exceed a threshold, and respective signatures are generated for the identified port scans that indicate the ports other than the high-traffic ports that were accessed in each of the port scans. A respective frequency of occurrence of each of the signatures over the set of the port scans is computed, and a whitelist of the signatures for which the respective frequency of occurrence is greater than a threshold is assembled. Upon detecting a port scan for which the respective signature is not whitelisted, a preventive action is initiated.

Abstract: Methods, apparatuses and computer program products implement embodiments of the present invention that include protecting a computer system by identifying multiple user identifiers associated with a single uses entity. A first event carried out using a first one of the user identifiers is detected. Upon detecting a second event carried out using a second one of the user identifiers that is different from the first one of the user identifiers, an alert can be issued in response to a combination of the first and the second events.

Abstract: Methods, apparatus and computer software products for protecting a computing system implement embodiments of the present invention that include extracting, from data traffic transmitted over a data network connecting a plurality of computing devices to multiple Internet hosting services, respective sets of transmissions from the computing devices to the Internet hosting services, and identifying, in a given set of the transmissions from a given computing device, multiple domain name system (DNS) requests for an identical second-level domain (2LD) and for different respective sub-domains within the 2LD. A number of the different sub-domains within the 2LD and a data size of the multiple DNS requests are computed, and when the number of the different sub-domains and the data size of the multiple DNS requests exceed a predefined criterion, a preventive action is initiated to inhibit DNS tunneling from at least the given computing device.

Abstract: Methods, apparatuses and computer program products implement embodiments of the present invention that include protecting a computing device by specifying one or more Internet sites that are accessible by one or more computing devices that communicate over a data network and identifying process binaries that executed on the computing devices accessed and retrieved data from any of the specified one more Internet sites. The identified process binaries are classified into a plurality of classes of matching process binaries, and for a given class, a count of the computing devices that that executed one of the process binaries of the given class is computed. When determining that the count of the computing devices is less than a predefined threshold, a preventive action is initiated to inhibit command and control (C2) channel transmissions from any of the computing devices that executed any of the process binaries of the given class.

Abstract: Methods, apparatus and computer software products implement embodiments of the present invention that include defining, for a given software category, respective, disjoint sets of communication ports that are used by each of a plurality of software systems in the given software category, including at least first and second disjoint sets. A set of port scans are identified in data traffic transmitted between multiple nodes that communicate over a network, each of the port scans including an access, in the data traffic, of a plurality of the communication ports on a given destination node by a given source node during a predefined time period. Upon detecting a port scan by one of the nodes including accesses of at least one of the communication ports in the first set and at least one of the communication ports in the second set, a preventive action is initiated.

Abstract: Methods, apparatus and computer software products implement embodiments of the present invention that include defining, for a given software category, respective, disjoint sets of communication ports that are used by each of a plurality of software systems in the given software category, including at least first and second disjoint sets. A set of port scans are identified in data traffic transmitted between multiple nodes that communicate over a network, each of the port scans including an access, in the data traffic, of a plurality of the communication ports on a given destination node by a given source node during a predefined time period. Upon detecting a port scan by one of the nodes including accesses of at least one of the communication ports in the first set and at least one of the communication ports in the second set, a preventive action is initiated.

Abstract: A method, including identifying, in network data traffic, multiple scans, each of the scans including an access, in the traffic, of multiple ports on a given destination node by a given source node during a time period. A group of high-traffic ports are identified in the traffic that include one or more ports that receive respective volumes of the traffic that exceed a threshold, and respective signatures are generated for the identified port scans that indicate the ports other than the high-traffic ports that were accessed in each of the port scans. A respective frequency of occurrence of each of the signatures over the set of the port scans is computed, and a whitelist of the signatures for which the respective frequency of occurrence is greater than a threshold is assembled. Upon detecting a port scan for which the respective signature is not whitelisted, a preventive action is initiated.

Abstract: Methods, apparatuses and computer program products implement embodiments of the present invention that include protecting a computing device by specifying one or more Internet sites that are accessible by one or more computing devices that communicate over a data network and identifying process binaries that executed on the computing devices accessed and retrieved data from any of the specified one more Internet sites. The identified process binaries are classified into a plurality of classes of matching process binaries, and for a given class, a count of the computing devices that that executed one of the process binaries of the given class is computed. When determining that the count of the computing devices is less than a predefined threshold, a preventive action is initiated to inhibit command and control (C2) channel transmissions from any of the computing devices that executed any of the process binaries of the given class.

Abstract: A method, including identifying, in network traffic during multiple periods, scans, each scan including an access of multiple ports on a given destination node by a given source node, and computing, for each given source in the scans, an average of destinations whose ports were accessed by the given source during any scan by the given source, and a fraction of periods when the given source accessed at least one of the destinations in at least one scan performed by the given source node. A whitelist is assembled sources for which one or more of the following conditions applies: the average of destinations accessed in the scans was greater than a first threshold, and the fraction of periods during which at least one destination was accessed in at least one scan was greater than a second threshold. Upon detecting a scan by any non-whitelisted node, a preventive action is initiated.

Abstract: A method, including identifying, in network data traffic, a set of pairs of source and destination nodes, each pair having a given source node, a given destination node, and one or more ports accessed in the traffic between the nodes in each pair, and computing, for each pair, a respective baseline that indicates a first number of the ports that source nodes other than the given source node in the pair accessed on the given destination node during a first period. For each pair, a respective test score is computed that indicates a difference between a second number of the ports that the given source node in the pair accessed on the given destination node during a second period and the baseline, and a preventive action is initiated with respect to the given source node in any of the pairs for which the test score is greater than a threshold.

Abstract: A method, including identifying, in network data traffic, a set of pairs of source and destination nodes, each pair having a given source node, a given destination node, and one or more ports accessed in the traffic between the nodes in each pair, and computing, for each pair, a respective baseline that indicates a first number of the ports that source nodes other than the given source node in the pair accessed on the given destination node during a first period. For each pair, a respective test score is computed that indicates a difference between a second number of the ports that the given source node in the pair accessed on the given destination node during a second period and the baseline, and a preventive action is initiated with respect to the given source node in any of the pairs for which the test score is greater than a threshold.

Abstract: A method, including identifying, in network data traffic, multiple scans, each of the scans including an access, in the traffic, of multiple ports on a given destination node by a given source node during a time period. A group of high-traffic ports are identified in the traffic that include one or more ports that receive respective volumes of the traffic that exceed a threshold, and respective signatures are generated for the identified port scans that indicate the ports other than the high-traffic ports that were accessed in each of the port scans. A respective frequency of occurrence of each of the signatures over the set of the port scans is computed, and a whitelist of the signatures for which the respective frequency of occurrence is greater than a threshold is assembled. Upon detecting a port scan for which the respective signature is not whitelisted, a preventive action is initiated.

Abstract: A method, including identifying, in network traffic during multiple periods, scans, each scan including an access of multiple ports on a given destination node by a given source node, and computing, for each given source in the scans, an average of destinations whose ports were accessed by the given source during any scan by the given source, and a fraction of periods when the given source accessed at least one of the destinations in at least one scan performed by the given source node. A whitelist is assembled sources for which one or more of the following conditions applies: the average of destinations accessed in the scans was greater than a first threshold, and the fraction of periods during which at least one destination was accessed in at least one scan was greater than a second threshold. Upon detecting a scan by any non-whitelisted node, a preventive action is initiated.

Abstract: Methods, apparatus and computer software products implement embodiments of the present invention that include protecting a computer system, by collecting information from data traffic transmitted between multiple local nodes on a private data network and public IP addresses corresponding to multiple remote nodes on a public data network. DNS resolutions are detected in the collected information, each DNS resolution identifying a local node requesting the resolution with respect to a URI and a public IP address corresponding to the URI. Transmissions from the local nodes to the public IP addresses are detected in the collected information at respective times, and the detected DNS resolutions are compared to the detected transmissions so as to identify the transmissions from the local notes to the public IP addresses that were not resolved by the DNS resolutions. Finally, a protective action is initiated with respect to at least some of the identified transmissions.

Abstract: Methods, apparatus and computer software products for protecting a computing system implement embodiments of the present invention that include extracting, from data traffic transmitted over a data network connecting a plurality of computing devices to multiple Internet hosting services, respective sets of transmissions from the computing devices to the Internet hosting services, and identifying, in a given set of the transmissions from a given computing device, multiple domain name system (DNS) requests for an identical second-level domain (2LD) and for different respective sub-domains within the 2LD. A number of the different sub-domains within the 2LD and a data size of the multiple DNS requests are computed, and when the number of the different sub-domains and the data size of the multiple DNS requests exceed a predefined criterion, a preventive action is initiated to inhibit DNS tunneling from at least the given computing device.

Abstract: A method, including identifying, in network data traffic, multiple scans, each of the scans including an access, in the traffic, of a plurality of ports on a given destination node by a given source node during a predefined period. Respective first probabilities of being accessed during any given scan computed for the communication ports that were accessed in the identified scans, and a respective second probability that both of the ports in the pair were accessed during any given scan are computed for each pair of the ports in the identified scans. Upon detecting a scan by one of the nodes including accesses of first and second ports on a given destination node for which the respective second probability for the pair of the first and second ports is lower than a threshold dependent upon the respective first probabilities of the first and second ports, a preventive action is initiated.