excel_xlm.yar

rule Excel_Hidden_Macro_Sheet
{
    meta:
        Author      = "InQuest Labs"
        URL         = "https://github.com/InQuest/yara-rules"
        Description = "http://blog.inquest.net/blog/2019/01/29/Carving-Sneaky-XLM-Files/"
    strings:
            $ole_marker     = {D0 CF 11 E0 A1 B1 1A E1}
            $macro_sheet_h1 = {85 00 ?? ?? ?? ?? ?? ?? 01 01}
            $macro_sheet_h2 = {85 00 ?? ?? ?? ?? ?? ?? 02 01}
    condition:
            $ole_marker at 0 and 1 of ($macro_sheet_h*)
}

rule SUSP_Excel4Macro_AutoOpen
{
    meta:
        description = "Detects Excel4 macro use with auto open / close"
        author = "John Lambert @JohnLaTwC"
        date = "2020-03-26"
        score = 50
        hash="2fb198f6ad33d0f26fb94a1aa159fef7296e0421da68887b8f2548bbd227e58f"
    strings:
        $header_docf = { D0 CF 11 E0 }
        $s1 = "Excel" fullword

        // 2fb198f6ad33d0f26fb94a1aa159fef7296e0421da68887b8f2548bbd227e58f
        // ' 0018     23 LABEL : Cell Value, String Constant - build-in-name 1 Auto_Open
        // 00002d80:
        // 20 00 00 01 07 00 00 00 00 00 00 00 00 00 00 01 3a 01 00 16 00 07 00

        // f4c01e26eb88b72d38be3d6331fafe03b1ae53fdbff57d610173ed797fa26e73
        // 00003460: 00 00 18 00 17 00 20 00 00 01 07 00 00 00 00 00  ...... .........
        // 00003470: 00 00 00 00 00 01 3a 00 00 3f 02 8d 00 c1 01 08  ......:..?......

        // ccef64586d25ffcb2b28affc1f64319b936175c4911e7841a0e28ee6d6d4a02d
        // ' 0018     23 LABEL : Cell Value, String Constant - build-in-name 1 Auto_Open
        // 00003560: 00 00 00 00 00 18 00 17 00 aa 03 00 01 07 00 00  ................
        // 00003570: 00 00 00 00 00 00 00 00 01 3a 00 00 04 00 65 00  .........:....e.

        $Auto_Open  = {18 00 17 00 20 00 00 01 07 00 00 00 00 00 00 00 00 00 00 01 3a }
        $Auto_Close = {18 00 17 00 20 00 00 01 07 00 00 00 00 00 00 00 00 00 00 02 3a }
        $Auto_Open1 = {18 00 17 00 aa 03 00 01 07 00 00 00 00 00 00 00 00 00 00 01 3a }
        $Auto_Close1= {18 00 17 00 aa 03 00 01 07 00 00 00 00 00 00 00 00 00 00 02 3a }

        // some Excel4 files don't have auto_open names e.g.:
        // b8b80e9458ff0276c9a37f5b46646936a08b83ce050a14efb93350f47aa7d269
        // 079be05edcd5793e1e3596cdb5f511324d0bcaf50eb47119236d3cb8defdfa4c


    condition:
        filesize < 400KB
        and $header_docf at 0
        and $s1
        and any of ($Auto_*)
}

Here's another xls doc with new Auto_Open string.
//$Auto_Open2 = {18 00 17 00 20 00 00 01 07 00 00 00 02 00 00 00 00 00 00 01 3a }
you can download from virustotal.
sha2: 1680252490e8ca347e25fa17f629569d22771ee11f36a2dd3fe07a9e1e624903