Baselining section is meant to assign all unassigned events to
cases, so that newly incoming events are immediately assigns to existing
cases and only differences to the last scan have to be reviewed. (new
malware, new signatures)
13.1.1. Auto Baselining
The Auto Baselining feature can be used to assign events to new and automatically generated cases. Auto Casing makes use of the so-called Auto Case ID, which is the same for all events of a certain type (see Glossary > Cases > Auto Case ID for details).
Auto Baselining is typically used to quickly reduce the remaining events in the Baselining section. It reduced the burden to manually group together events of a similar type.
Automatically cased events can then be reviewed in the
Auto Baselining uses a threshold that defines the minimum number of events required in each of these automatically generated cases. A threshold of 10 instructs the process to create only cases for groups of at least 10 similar events. Obviously, we do not recommend using threshold of 1, but everything higher than 1 can be reasonable.
The best practice is to start the Auto Baselining process with a relatively high threshold (e.g., 10) and then subsequently perform iterations with lower thresholds.
The Optimization is used to assign unassigned events to cases based on their filters.
Usually, an analyst selects events and creates a case with these events. During the case creation a set of filters gets generated to automatically assign newly incoming events to this case.
Often, characteristics of existing older events also align with the criteria described in the filters of the new case. However, they do not get assigned to that case, because they’re already in the database and the case assignment only happens when new events arrive.
Optimization is used to assign unassigned events to existing cases.
13.2.1. Auto Case ID (formerly Group ID)
The Auto Case ID is an automatically generated ID for a group of events.
This group has been formed automatically by the use filters generated from predefined filter templates (see Glossary > Invisible > Filter Templates).
Auto Case IDs identify a groupable set of events.
The Auto Case IDs are used in case creation as the default method to
assign new events to a case. You can review the Auto Case IDs used to
assign new events to a case in the Tab
Grouping Criteria of each case.
They are also used in "Auto Casing" and "Optimization". (see Glossary > Baselining)
13.2.2. Dynamic Auto Case ID
The Dynamic Auto Case IDs are generated for events that don’t have a corresponding filter template defined. This is often the case for very rare event types or events of a low level (Info, Notice).
You can think of them as a fallback in form of a less efficient grouping method.
They are usually created of all fields of an event except the ones that are highly specific, like the HOSTNAME field.
If your case uses many Dynamic Auto Case IDs, distinguishable by the leading uppercase "D", then automatic event assignment is nearly impossible. In these cases, you should rather use a string conditions to group events into that case and assign new incoming events automatically.
13.2.3. Filter Priority
It is possible that two or more cases include filters that would assign a new incoming event to them. This often happens when one case uses Auto Case ID (see Glossary section) and another case uses a string selection (String Condition).
The filter priority can be used to prioritize the filters of a case so that newly incoming events go to that prioritized case and not the one with the default priority.
You could also create fallback cases, e.g., for all events of the level "Notice" and intentionally reduce the priority of this case so that other cases that select events of that level always come first.
The full prioritization process looks like:
Case with higher priority takes the event
If both cases have the same priority, the case with the higher "Type" takes the event (Incident > Noteworthy)
If both cases have the same priority and the same type, the case with the smaller case ID (older case) takes the events
13.2.4. External ID
This field is optional and can be used to refer to an ID that you use in a different system, like a ticket management system or an incident response platform.
13.2.5. Difference between Summary and Assessment
Summary is meant to include the elements (fields) of events
that are used as characteristics to perform an assessment. You can think
of it as the values that you as an analyst want to highlight for other
analysts that review that specific case. It’s often a special file name
and location or a process name and YARA rule match on that process.
You can use the "Auto Summary" feature to get an auto-recommended content for this field.
Assessment is the one that requires the most effort. It
contains the findings of the analyst’s review.
13.2.6. Case Types
The following table describes the cases types taxonomy used in Analysis Cockpit.
Incident cases report a clear threat, indicated by a hard match and verified by
research of an analyst. Analysts create incident cases to indicate the highest possible
certainty and risk. Incident cases are also characterized by the fact that they
do not need to be verified by someone else. They either indicate malware, a threat
group or penetration testing activity and should trigger immediate response.
Suspicious cases are based on significant indicators that require a review by
someone within the organization or more evidence to come to a final conclusion.
Often, file samples or process memory dumps are required to verify/falsify a
verdict. Cases of this type usually trigger evidence collection or review actions.
Noteworthy cases are based on soft indicators or elements that should be
reviewed whenever there is time to do that. They include all kinds of events that
cannot be dismissed as false positives or anomalies but are likely uncritical.
Noteworthy cases don’t trigger an immediate response but should be reviewed
whenever there is time to do that.
Vulnerability cases contain detected software or configuration weaknesses that
compromise system integrity. The reported vulnerabilities often include easy to exploit
weaknesses that are frequently used by threat groups to execute code remotely,
gain access or escalate privileges on affected systems. Cases classified as
Vulnerability are typically integrated into a vulnerability management process
as an additional input channel.
Legitimate Anomaly cases contain events that are related to legitimate elements
that are suspicious, but an ordinary finding in the context of the analyzed organization.
The reason for an anomaly is not a malfunction of the scanner but a
peculiarity within the analyzed environment. Legitimate Anomalies don’t trigger
any further activity.
False Positive cases contain events that indicate suspicious or malicious activity,
but the review revealed that it is actually legitimate software or other elements.
The only reason for a false positive is a scanner malfunction or signatures that
falsely report a threat (see section 13.2.7. for more details). A false positive
usually triggers a review by Nextron Systems and a signature adjustment.
The default state of newly created cases.
13.2.7. Difference between False Positive and Legitimate Anomaly
We use "False Positive" and "Legitimate Anomaly" to distinguish between situations in which the scanner (THOR) made an error and situations in which a customer environment contains suspicious or malicious elements that are known.
E.g., a Winrar used by admins as "r.exe" in "C:\users\public" for software rollout purposes is not considered a "False Positive" but a "Legitimate Anomaly". It is a finding which doesn’t have to be fixed in THOR’s signature set but is simply a specific situation in the analyzed environment.
Matches that are clearly an error in THOR signatures should be classified as "False Positive".
Examples for "Legitimate Anomalies":
Suspicious RUN Key entries that use customer software
Custom software that uses suspicious folders, e.g. C:\Users\Public, %AppData%
Process memory match with a "ReflectiveLoader" YARA rule on a third party EDR agent process
Examples for "False Positives":
YARA rule match on Bloomberg or SAP software
Filename IOC match "w64.exe" on a Perl for Windows build tool
YARA rule match with "Putty_Anomaly" on a legitimate and signed putty.exe
Another good example is one of the many anomaly signatures that triggers on an XORed MS-DOS Stub. A match with such a signature only qualifies as false positives when there is no XORed MS-DOS stub in that file and not when it turns out to be a legitimate file. The signature detects what it is designed to detect.
A signature with a rule named MAL_Xrat_Mar21_1 that triggers on a legitimate and signed executable, however, is a false positive.
13.3. Invisible (Backend)
13.3.1. Filter Templates
The Analysis Cockpit uses so-called filter templates that describe which fields in which event types are specific enough to be used in a filter that can be used to automatically group events.
These groups can be identified by a common so-called "Auto Case ID" (formerly Group ID). See the respective entry in this Glossary.
The filter templates are static and predefined.
E.g., a typical filter template states that for events in the Module "Filescan", the fields FILE and SHA1 are sufficiently specific to group events based on equal values in these two fields.