Microsoft has published a set of new security functions (user-defined) in KQL. These are focused on the graph mindset, meaning relationships between nodes (objects). A previous blogpost explains graph semantics a bit more:
Graph semantics in Kusto – SEC-LABS R&D
The new functions released has many goodies, such as calculating blast radius, exposure perimeter and much more
User-defined functions can be saved as functions in Defender XDR or executed within the query itself.
| Function Name | Description |
|---|---|
| detect_anomalous_new_entity_fl() | Detect the appearance of anomalous new entities in timestamped data. |
| detect_anomalous_spike_fl() | Detect the appearance of anomalous spikes in numeric variables in timestamped data. |
| graph_blast_radius_fl() | Calculate the Blast Radius (list and score) of source nodes over path or edge data. |
| graph_exposure_perimeter_fl() | Calculate the Exposure Perimeter (list and score) of target nodes over path or edge data. |
| graph_node_centrality_fl() | Calculate various metrics of node centrality (such as degree and betweenness) over graph data (edge and nodes). |
| graph_path_discovery_fl() | Discover valid paths between relevant endpoints (sources and targets) over graph data (edge and nodes). |
Example query (with defined table as input) from learn
let edges = datatable (SourceNodeName:string, EdgeName:string, EdgeType:string, TargetNodeName:string, Region:string)[
'vm-work-1', 'e1', 'can use', 'webapp-prd', 'US',
'vm-custom', 'e2', 'can use', 'webapp-prd', 'US',
'webapp-prd', 'e3', 'can access', 'vm-custom', 'US',
'webapp-prd', 'e4', 'can access', 'test-machine', 'US',
'vm-custom', 'e5', 'can access', 'server-0126', 'US',
'vm-custom', 'e6', 'can access', 'hub_router', 'US',
'webapp-prd', 'e7', 'can access', 'hub_router', 'US',
'test-machine', 'e8', 'can access', 'vm-custom', 'US',
'test-machine', 'e9', 'can access', 'hub_router', 'US',
'hub_router', 'e10', 'routes traffic to', 'remote_DT', 'US',
'vm-work-1', 'e11', 'can access', 'storage_main_backup', 'US',
'hub_router', 'e12', 'routes traffic to', 'vm-work-2', 'US',
'vm-work-2', 'e13', 'can access', 'backup_prc', 'US',
'remote_DT', 'e14', 'can access', 'backup_prc', 'US',
'backup_prc', 'e15', 'moves data to', 'storage_main_backup', 'US',
'backup_prc', 'e16', 'moves data to', 'storage_DevBox', 'US',
'device_A1', 'e17', 'is connected to', 'sevice_B2', 'EU',
'sevice_B2', 'e18', 'is connected to', 'device_A1', 'EU'
];
let nodes = datatable (NodeName:string, NodeType:string, NodeEnvironment:string, Region:string) [
'vm-work-1', 'Virtual Machine', 'Production', 'US',
'vm-custom', 'Virtual Machine', 'Production', 'US',
'webapp-prd', 'Application', 'None', 'US',
'test-machine', 'Virtual Machine', 'Test', 'US',
'hub_router', 'Traffic Router', 'None', 'US',
'vm-work-2', 'Virtual Machine', 'Production', 'US',
'remote_DT', 'Virtual Machine', 'Production', 'US',
'backup_prc', 'Service', 'Production', 'US',
'server-0126', 'Server', 'Production', 'US',
'storage_main_backup', 'Cloud Storage', 'Production', 'US',
'storage_DevBox', 'Cloud Storage', 'Test', 'US',
'device_A1', 'Device', 'Backend', 'EU',
'device_B2', 'Device', 'Backend', 'EU'
];
let nodesEnriched = (
nodes
| extend IsValidStart = (NodeType == 'Virtual Machine'), IsValidEnd = (NodeType == 'Cloud Storage') // option 1
//| extend IsValidStart = (NodeName in('vm-work-1', 'vm-work-2')), IsValidEnd = (NodeName in('storage_main_backup')) // option 2
//| extend IsValidStart = (NodeEnvironment == 'Test'), IsValidEnd = (NodeEnvironment == 'Production') // option 3
);
let graph_path_discovery_fl = ( edgesTableName:string, nodesTableName:string, scopeColumnName:string
, isValidPathStartColumnName:string, isValidPathEndColumnName:string
, nodeIdColumnName:string, edgeIdColumnName:string, sourceIdColumnName:string, targetIdColumnName:string
, minPathLength:long = 1, maxPathLength:long = 8, resultCountLimit:long = 100000)
{
let edges = (
table(edgesTableName)
| extend sourceId = column_ifexists(sourceIdColumnName, '')
| extend targetId = column_ifexists(targetIdColumnName, '')
| extend edgeId = column_ifexists(edgeIdColumnName, '')
| extend scope = column_ifexists(scopeColumnName, '')
);
let nodes = (
table(nodesTableName)
| extend nodeId = column_ifexists(nodeIdColumnName, '')
| extend isValidPathStart = column_ifexists(isValidPathStartColumnName, '')
| extend isValidPathEnd = column_ifexists(isValidPathEndColumnName, '')
| extend scope = column_ifexists(scopeColumnName, '')
);
let paths = (
edges
// Build graph object partitioned by scope, so that no connections are allowed between scopes.
// In case no scopes are relevant, partitioning should be removed for better performance.
| make-graph sourceId --> targetId with nodes on nodeId partitioned-by scope (
// Look for existing paths between source nodes and target nodes with less than predefined number of hops
// Current configurations looks for directed paths without any cycles; this can be changed if needed
graph-match cycles = none (s)-[e*minPathLength..maxPathLength]->(t)
// Filter only by paths with that connect valid endpoints
where ((s.isValidPathStart) and (t.isValidPathEnd))
project sourceId = s.nodeId
, isSourceValidPathStart = s.isValidPathStart
, targetId = t.nodeId
, isTargetValidPathEnd = t.isValidPathEnd
, scope = s.scope
, edgeIds = e.edgeId
, edgeAllTargetIds = e.targetId
| limit resultCountLimit
)
| extend pathLength = array_length(edgeIds)
, pathId = hash_md5(strcat(sourceId, strcat(edgeIds), targetId))
, pathAllNodeIds = array_concat(pack_array(sourceId), edgeAllTargetIds)
| project-away edgeAllTargetIds
| mv-apply with_itemindex = SortIndex nodesInPath = pathAllNodeIds to typeof(string), edgesInPath = edgeIds to typeof(string) on (
extend step = strcat(
iff(isnotempty(nodesInPath), strcat('(', nodesInPath, ')'), '')
, iff(isnotempty(edgesInPath), strcat('-[', edgesInPath, ']->'), ''))
| summarize fullPath = array_strcat(make_list(step), '')
)
);
paths
};
graph_path_discovery_fl(edgesTableName = 'edges'
, nodesTableName = 'nodesEnriched'
, scopeColumnName = 'Region'
, nodeIdColumnName = 'NodeName'
, edgeIdColumnName = 'EdgeName'
, sourceIdColumnName = 'SourceNodeName'
, targetIdColumnName = 'TargetNodeName'
, isValidPathStartColumnName = 'IsValidStart'
, isValidPathEndColumnName = 'IsValidEnd'
)Happy Hunting!