You'd need to change the query that collects the source nodes to read like this:
MATCH (attack:SyntheticRequest)-[:COUNTERMEASURE_SUCCESS]->(c:SyntheticCountermeasure)
WHERE attack.url contains 'attack1'
WITH collect(c) AS sourceNodes
call gds.pageRank.stream('threat', {
sourceNodes: sourceNodes,
relationshipWeightProperty: 'weight'
})
YIELD nodeId, score
WHERE score > 0
RETURN nodeId,gds.util.asNode(nodeId).name AS name, score
ORDER BY score DESC