diff --git a/detection-rules/link_issuu_unsolicited.yml b/detection-rules/link_issuu_unsolicited.yml new file mode 100644 index 00000000000..a713b6b15a3 --- /dev/null +++ b/detection-rules/link_issuu_unsolicited.yml @@ -0,0 +1,57 @@ +name: "Link: Issuu Link from Unsolicited Sender" +description: "This detection rule matches on messaging containing at least one link to issuu..com from an unsolicited sender. issuu.com provides a free plan enabling users to create custom flipbooks and file hosting. This services has been abused by threat actors to host landing pages directing victims to a next stage of credential phishing." +type: "rule" +severity: "medium" +source: | + type.inbound + and any(filter(body.links, + // issuu link + .href_url.domain.root_domain == 'issuu.com' + and strings.icontains(.href_url.path, "/docs/") + ), + ( + .href_url.query_params is null + // reduce alerting on newsletters, flyers, etc + // by ensure there are not any marketing focused query param keys like utm_source + or regex.imatch(.href_url.query_params, '^fr=[^\&]+$') + ) + ) + + // to further reduce noise from newsletters/flyers inspect the number of imbedded images + and strings.icount(body.html.raw, '