Yara Hexadecimal String

You can just find these with xxd

Fixed Length

strings:
	$mz = {4d 5a}

Array with Arbitrary Sequence

strings:
	// jump assembly instruction, match any address 4-6 bytes long
    $hex_string = { F4 23 [4-6] 62 B4 }

Will match any of these:

strings:
	// jump assembly instruction, match any address 6 bytes long
    $hex_string = { F4 23 [6] 62 B4 }

Array with Wildcard

strings:
	// match a specific byte sequence wiht a wildcard
	$arr_with_wildcard = {70 74 ?? 25 3E}