規則撰寫建議

規則撰寫建議

1. 在可能的情況下，請務必指定 Channel 或 ProviderName 名稱以及 EventID 編號。 預設情況下，只有列在 ./rules/config/target_event_IDs.txt 中的事件 ID 才會被掃描，因此如果該 EID 尚未在此檔案中，您可能需要將新的 EventID 編號加入此檔案。

2. 在不需要時，請勿使用多個 selection 或 filter 欄位以及過度的分組。 例如：

不要這樣做

detection:
    SELECTION_1:
        Channnel: Security
    SELECTION_2:
        EventID: 4625
    SELECTION_3:
        LogonType: 3
    FILTER_1:
        SubStatus: "0xc0000064"   #Non-existent user
    FILTER_2:
        SubStatus: "0xc000006a"   #Wrong password
    condition: SELECTION_1 and SELECTION_2 and SELECTION_3 and not (FILTER_1 or FILTER_2)

請這樣做

detection:
    selection:
        Channel: Security
        EventID: 4625
        LogonType: 3
    filter:
        - SubStatus: "0xc0000064"   #Non-existent user
        - SubStatus: "0xc000006a"   #Wrong password
    condition: selection and not filter

1. 當您需要多個區段時，請將第一個包含 channel 與 event ID 資訊的區段命名為 section_basic 區段，並將其他選擇條件以有意義的名稱命名於 section_ 與 filter_ 之後。此外，請撰寫註解來解釋任何難以理解之處。 例如：

不要這樣做

detection:
    Takoyaki:
        Channel: Security
        EventID: 4648
    Naruto:
        TargetUserName|endswith: "$"
        IpAddress: "-"
    Sushi:
        SubjectUserName|endswith: "$"
        TargetUserName|endswith: "$"
        TargetInfo|endswith: "$"
    Godzilla:
        SubjectUserName|endswith: "$"
    Ninja:
        TargetUserName|re: "(DWM|UMFD)-([0-9]|1[0-2])$"
        IpAddress: "-"
    Daisuki:
        - ProcessName|endswith: "powershell.exe"
        - ProcessName|endswith: "WMIC.exe"
    condition: Takoyaki and Daisuki and not (Naruto and not Godzilla) and not Ninja and not Sushi

請這樣做

detection:
    selection_basic:
        Channel: Security
        EventID: 4648
    selection_TargetUserIsComputerAccount:
        TargetUserName|endswith: "$"
        IpAddress: "-"
    filter_UsersAndTargetServerAreComputerAccounts:     #Filter system noise
        SubjectUserName|endswith: "$"
        TargetUserName|endswith: "$"
        TargetInfo|endswith: "$"
    filter_SubjectUserIsComputerAccount:
        SubjectUserName|endswith: "$"
    filter_SystemAccounts:
        TargetUserName|re: "(DWM|UMFD)-([0-9]|1[0-2])$" #Filter out default Desktop Windows Manager and User Mode Driver Framework accounts
        IpAddress: "-"                                  #Don't filter if the IP address is remote to catch attackers who created backdoor accounts that look like DWM-12, etc..
    selection_SuspiciousProcess:
        - ProcessName|endswith: "powershell.exe"
        - ProcessName|endswith: "WMIC.exe"
    condition: selection_basic and selection_SuspiciousProcess and not (selection_TargetUserIsComputerAccount
               and not filter_SubjectUserIsComputerAccount) and not filter_SystemAccounts and not filter_UsersAndTargetServerAreComputerAccounts

將 Sigma 規則轉換為 Hayabusa 格式

我們建立了一個後端，可將規則從 Sigma 轉換為 Hayabusa 相容格式，請參見此處。