COM Event System Loading New DLL

Original query, unchanged.

let lookback_start = 7d;
let lookback_end = 1d;
let timedelta = 5s;
// Get a list of previously seen DLLs being loaded
let known_dlls = (Event
| where TimeGenerated between(ago(lookback_start)..ago(lookback_end))
| where EventID == 7
| extend EvData = parse_xml(EventData)
| extend EventDetail = EvData.DataItem.EventData.Data
| extend LoadedItems = parse_json(tostring(parse_json(tostring(EvData.DataItem)).EventData)).["Data"]
| mv-expand LoadedItems
| where tostring(LoadedItems.["@Name"]) =~ "ImageLoaded"
| extend DLL = tostring(LoadedItems.["#text"])
| summarize by DLL);
// Get Image Load events related to svchost.exe
Event
| where Source =~ "Microsoft-Windows-Sysmon"
// Image Load Event in Sysmon
| where EventID == 7
| extend EvData = parse_xml(EventData)
| extend EventDetail = EvData.DataItem.EventData.Data
| extend Images = parse_json(tostring(parse_json(tostring(EvData.DataItem)).EventData)).["Data"]
| mv-expand Images
// Parse out executing process
| where tostring(Images.["@Name"]) =~ "Image"
| extend Image = tostring(Images.["#text"])
| where Image endswith "\\svchost.exe"
// Parse out loaded DLLs
| extend LoadedItems = parse_json(tostring(parse_json(tostring(EvData.DataItem)).EventData)).["Data"]
| mv-expand LoadedItems
| where tostring(LoadedItems.["@Name"]) =~ "ImageLoaded"
| extend DLL = tostring(LoadedItems.["#text"])
| extend Image = tostring(Image)
| extend ImageLoadTime = TimeGenerated
// Join with processes with a command line related to COM Event System
| join kind = inner(Event
| where Source =~ "Microsoft-Windows-Sysmon"
// Sysmon process execution events
| where EventID == 1
| extend RenderedDescription = tostring(split(RenderedDescription, ":")[0])
| extend EventData = parse_xml(EventData).DataItem.EventData.Data
| mv-expand bagexpansion=array EventData
| evaluate bag_unpack(EventData)
| extend Key = tostring(column_ifexists('@Name', "")), Value = column_ifexists('#text', "")
| evaluate pivot(Key, any(Value), TimeGenerated, Source, EventLog, Computer, EventLevel, EventLevelName, EventID, UserName, RenderedDescription, MG, ManagementGroupName, Type, _ResourceId)
| extend ParentImage = tostring(column_ifexists("ParentImage", "NotAvailable"))
// Command line related to COM Event System
| where ParentImage endswith "\\svchost.exe"
//| where ParentCommandLine has_all (" -k LocalService"," -p"," -s EventSystem")
| extend ProcessExecutionTime = TimeGenerated) on $left.Image == $right.ParentImage
// Check timespan between DLL load and process creation
| extend delta =  ProcessExecutionTime - ImageLoadTime
| where ImageLoadTime <= ProcessExecutionTime and delta <= timedelta
// Filter to only newly seen DLLs
| where DLL !in (known_dlls)
| extend ParentCommandLine = tostring(column_ifexists("ParentCommandLine", "NotAvailable"))
| project-reorder ImageLoadTime, ProcessExecutionTime , Image, ParentCommandLine, DLL
| extend Hashes = tostring(column_ifexists("Hashes", "NotAvailable, NotAvailable"))
| extend Hashes = split(Hashes, ",")
| mv-apply Hashes on (summarize FileHashes = make_bag(pack(tostring(split(Hashes, "=")[0]), tostring(split(Hashes, "=")[1]))))
| extend SHA1 = tostring(FileHashes.SHA1)
| extend HashAlgo = "SHA1"
| extend HostName = tostring(split(Computer, ".")[0]), DomainIndex = toint(indexof(Computer, '.'))
| extend HostNameDomain = iff(DomainIndex != -1, substring(Computer, DomainIndex + 1), Computer)
| extend Name = tostring(split(UserName, "\\")[1]), NTDomain = tostring(split(UserName, "\\")[0])