diff --git a/apigetpost.py b/apigetpost.py
index bbd594ca413..0bbcf5f8641 100644
--- a/apigetpost.py
+++ b/apigetpost.py
@@ -16,6 +16,7 @@ def __init__(self):
         self.owner_url = None
         self.owner_name = None
         self.owner_rep = None
+        self.owner_acct_id = None
         self.title = None
         self.body = None
         self.body_markdown = None
@@ -33,7 +34,12 @@ def as_dict(self):
             'title': self.title,
             'body': self.body,
             'body_markdown': self.body_markdown,
-            'owner': {'display_name': self.owner_name, 'link': self.owner_url, 'reputation': self.owner_rep},
+            'owner': {
+                'display_name': self.owner_name,
+                'link': self.owner_url,
+                'reputation': self.owner_rep,
+                'account_id': self.owner_acct_id
+            },
             'site': self.site,
             'question_id': self.post_id,
             'link': self.post_url,
@@ -82,6 +88,7 @@ def api_get_post(post_url):
         post_data.owner_name = html.unescape(item['owner']['display_name'])
         post_data.owner_url = item['owner']['link']
         post_data.owner_rep = item['owner']['reputation']
+        post_data.owner_acct_id = item['owner']['account_id']
     else:
         post_data.owner_name = ""
         post_data.owner_url = ""
diff --git a/chatcommands.py b/chatcommands.py
index f80f1f42e2d..32e8114708b 100644
--- a/chatcommands.py
+++ b/chatcommands.py
@@ -71,13 +71,87 @@ def addblu(msg, user):
         message_url = "https://chat.{}/transcript/{}?m={}".format(msg._client.host, msg.room.id, msg.id)
 
         add_blacklisted_user((uid, val), message_url, "")
-        return "User blacklisted (`{}` on `{}`).".format(uid, val)
+        return f"User blacklisted {'network-wide ' if val == 'stackexchange.com' else ''}(`{uid}` on `{val}`)."
     elif int(uid) == -2:
         raise CmdException("Error: {}".format(val))
     else:
         raise CmdException("Invalid format. Valid format: `!!/addblu profileurl` *or* `!!/addblu userid sitename`.")
 
 
+def user_to_net_acct_id(user: tuple[str, str]) -> str:
+    """Find the network account ID of a user (e.g., a site profile)"""
+    uid, val = user
+
+    # SE user passed
+    if val == "stackexchange.com":
+        return uid
+    # network user passed
+    else:
+        # based on the allspam code
+        with GlobalVars.api_request_lock:
+            if GlobalVars.api_backoff_time > time.time():
+                time.sleep(GlobalVars.api_backoff_time - time.time() + 2)
+            request_url = get_se_api_url_for_route(f"users/{uid}")
+            params = get_se_api_default_params({
+                'filter': '!)scNT2zLcbOpD09vBxHM',
+                'site': val
+            })
+            res = requests.get(request_url, params=params, timeout=GlobalVars.default_requests_timeout).json()
+            if "backoff" in res:
+                if GlobalVars.api_backoff_time < time.time() + res["backoff"]:
+                    GlobalVars.api_backoff_time = time.time() + res["backoff"]
+        if 'items' not in res or len(res['items']) == 0:
+            raise CmdException("The specified user does not appear to exist.")
+        return str(res['items'][0]['account_id'])
+
+
+def is_user_net_blacklisted(user: tuple[str, str]) -> bool:
+    """Given a user ID and a site, return if they are network-blacklisted"""
+    return (user_to_net_acct_id(user), 'stackexchange.com') in GlobalVars.blacklisted_users
+
+
+@command(str, whole_msg=True, privileged=True)
+def addnetblu(msg, user):
+    """
+    Adds a user to the network-wide blacklist
+    :return: A string
+    """
+    uid, val = get_user_from_list_command(user)
+
+    if int(uid) > -1 and val != "":
+        message_url = "https://chat.{}/transcript/{}?m={}".format(msg._client.host, msg.room.id, msg.id)
+        net_id: str = user_to_net_acct_id((uid, val))
+        add_blacklisted_user((net_id, "stackexchange.com"), message_url, "")
+        return f"User blacklisted network-wide (`{net_id}`)."
+    elif int(uid) == -2:
+        raise CmdException("Error: {}".format(val))
+    else:
+        raise CmdException("Invalid format. Valid format: `!!/addnetblu profileurl` *or* "
+                           "`!!/addnetblu userid stackexchange.com`.")
+
+
+@command(str, privileged=True)
+def rmnetblu(user):
+    """
+    Removes user from the network-wide blacklist
+    :param user:
+    :return: A string
+    """
+    uid, val = get_user_from_list_command(user)
+
+    if int(uid) > -1 and val != "":
+        net_id: str = user_to_net_acct_id((uid, val))
+        if remove_blacklisted_user((net_id, "stackexchange.com")):
+            return f"The user has been removed from the network-wide user-blacklist (`{net_id}`)."
+        else:
+            return "The user is not network-wide blacklisted."
+    elif int(uid) == -2:
+        raise CmdException("Error: {}".format(val))
+    else:
+        raise CmdException("Invalid format. Valid format: `!!/rmnetblu profileurl` "
+                           "*or* `!!/rmnetblu userid stackexchange.com`.")
+
+
 # noinspection PyIncorrectDocstring,PyMissingTypeHints
 @command(str)
 def isblu(user):
@@ -90,10 +164,26 @@ def isblu(user):
     uid, val = get_user_from_list_command(user)
 
     if int(uid) > -1 and val != "":
-        if is_blacklisted_user((uid, val)):
-            return "User is blacklisted (`{}` on `{}`).".format(uid, val)
+        is_site_wide: bool = is_blacklisted_user((uid, val))
+        is_network_wide: bool = is_user_net_blacklisted((uid, val))
+        is_se_acct: bool = val == "stackexchange.com"
+        # It could check what sites a user is blacklisted on, even if that
+        # site isn't passed. That functionality could be useful, but I didn't
+        # write the code to do that.
+        if is_se_acct and is_network_wide:
+            return "User is blacklisted network-wide"
+        elif is_se_acct and not is_network_wide:
+            return "User is not blacklisted network-wide"
+        elif is_site_wide and is_network_wide:
+            return f"User is blacklisted both on `{val}` (`{uid}`) and network-wide"
+        elif is_site_wide and not is_network_wide:
+            return f"User is blacklisted on `{val}` (`{uid}`), but not network-wide"
+        elif not is_site_wide and is_network_wide:
+            return f"User is blacklisted network-wide, but not on `{val}` (`{uid}`)"
+        elif not is_site_wide and not is_network_wide:
+            return f"User is neither blacklisted on `{val}` (`{uid}`) nor network-wide"
         else:
-            return "User is not blacklisted (`{}` on `{}`).".format(uid, val)
+            return "This should never be reached"
     elif int(uid) == -2:
         raise CmdException("Error: {}".format(val))
     else:
@@ -111,8 +201,9 @@ def rmblu(user):
     uid, val = get_user_from_list_command(user)
 
     if int(uid) > -1 and val != "":
+        net_wide: str = "network-wide " if (val == "stackexchange.com") else ""
         if remove_blacklisted_user((uid, val)):
-            return "The user has been removed from the user-blacklist (`{}` on `{}`).".format(uid, val)
+            return "The user has been removed from the {}user-blacklist (`{}` on `{}`).".format(net_wide, uid, val)
         else:
             return "The user is not blacklisted. Perhaps they have already been removed from the blacklist. Please " \
                    "see: [Blacklists, watchlists, and the user-whitelist: User-blacklist and user-whitelist]" \
diff --git a/classes/_Post.py b/classes/_Post.py
index f9005ce0208..07ec4c0e093 100644
--- a/classes/_Post.py
+++ b/classes/_Post.py
@@ -2,7 +2,7 @@
 import json
 from helpers import log
 import html
-from typing import AnyStr, Union
+from typing import AnyStr, Union, Optional
 
 
 class PostParseError(Exception):
@@ -31,6 +31,7 @@ def __init__(self, json_data=None, api_response=None, parent=None):
         self._user_url = ""
         self._votes = {'downvotes': None, 'upvotes': None}
         self._edited = False
+        self._owner_account_id = None
 
         if parent is not None:
             if not isinstance(parent, Post):
@@ -143,7 +144,8 @@ def _parse_api_post(self, response):
             'owner': {
                 'display_name': '_user_name',
                 'link': '_user_url',
-                'reputation': '_owner_rep'
+                'reputation': '_owner_rep',
+                'account_id': '_owner_account_id'
             },
             'question_id': '_post_id',
             'answer_id': '_post_id',
@@ -221,6 +223,9 @@ def post_id(self):
     def post_score(self):
         return int(self._post_score)
 
+    def get_account_id(self) -> Optional[int]:
+        return int(self._owner_account_id) if self._owner_account_id is not None else None
+
     @property
     def post_site(self):
         if type(self._post_site) in [bytes, bytearray]:
diff --git a/globalvars.py b/globalvars.py
index 632cf9eb935..0f07c8f5b77 100644
--- a/globalvars.py
+++ b/globalvars.py
@@ -173,7 +173,7 @@ class GlobalVars:
     # accurately from the correct route. However, for scanning posts, we also want the question data associated
     # with an answer.
     se_api_question_answer_post_filter = \
-        "!scxINmJWAnjuckNJkP9YfbG196DrCj)DDXQjRKUGfp-QzZ3b1nRh1Qitw7)FdyW_)iLrL8TBxFYZ1"
+        "!*b8DH81UdVw)kQyIDQMTMc9jrRZh7*x*46g(fPTyFh)C2d3Fp9kSnnFDHyiG5L3cG39qg66pgP63xLa74Uq"
     se_api_url_base = "https://api.stackexchange.com/2.4/"
     se_api_default_params = {
         'key': 'IAkbitmze4B8KpacUfLqkw((',
diff --git a/spamhandling.py b/spamhandling.py
index 764fb91d2b9..37b11d7ad0a 100644
--- a/spamhandling.py
+++ b/spamhandling.py
@@ -43,10 +43,19 @@ def sum_weight(reasons: list):
     return s
 
 
+def is_post_owner_net_blacklisted(post: Post) -> bool:
+    """Check if the owner of a post is network-wide blacklisted"""
+    for acct_id, site in GlobalVars.blacklisted_users.keys():
+        if int(acct_id) == post.get_account_id() and site == "stackexchange.com":
+            return True
+    return False
+
+
 # noinspection PyMissingTypeHints
 def check_if_spam(post, dont_ignore_for=None):
     test, why = findspam.FindSpam.test_post(post)
-    if datahandling.is_blacklisted_user(parsing.get_user_from_url(post.user_url)):
+    net_blacklisted: bool = is_post_owner_net_blacklisted(post)
+    if datahandling.is_blacklisted_user(parsing.get_user_from_url(post.user_url)) or net_blacklisted:
         test.append("blacklisted user")
         blacklisted_user_data = datahandling.get_blacklisted_user_data(parsing.get_user_from_url(post.user_url))
         if len(blacklisted_user_data) > 1:
@@ -62,6 +71,8 @@ def check_if_spam(post, dont_ignore_for=None):
                 ms_url = datahandling.resolve_ms_link(rel_url) or to_metasmoke_link(rel_url)
                 why += "\nBlacklisted user - blacklisted for {} ({}) by {}".format(
                     blacklisted_post_url, ms_url, blacklisted_by)
+            if net_blacklisted:
+                why += f"\nNetwork-wide blacklisted user - blacklisted by {blacklisted_by}"
             else:
                 why += "\n" + u"Blacklisted user - blacklisted by {}".format(blacklisted_by)
     if test:
diff --git a/test/test_chatcommands.py b/test/test_chatcommands.py
index af2ac8bf64b..8ee7631b0fe 100644
--- a/test/test_chatcommands.py
+++ b/test/test_chatcommands.py
@@ -589,16 +589,16 @@ def test_blacklisted_users():
 
         # Format: !!/*blu profileurl
         assert chatcommands.isblu("https://stackoverflow.com/users/4622463/angussidney", original_msg=msg) == \
-            "User is not blacklisted (`4622463` on `stackoverflow.com`)."
+            "User is neither blacklisted on `stackoverflow.com` (`4622463`) nor network-wide"
         assert chatcommands.addblu("https://stackoverflow.com/users/4622463/angussidney", original_msg=msg) == \
             "User blacklisted (`4622463` on `stackoverflow.com`)."
         # TODO: Edit command to check and not blacklist again, add test
         assert chatcommands.isblu("https://stackoverflow.com/users/4622463/angussidney", original_msg=msg) == \
-            "User is blacklisted (`4622463` on `stackoverflow.com`)."
+            "User is blacklisted on `stackoverflow.com` (`4622463`), but not network-wide"
         assert chatcommands.rmblu("https://stackoverflow.com/users/4622463/angussidney", original_msg=msg) == \
             "The user has been removed from the user-blacklist (`4622463` on `stackoverflow.com`)."
         assert chatcommands.isblu("https://stackoverflow.com/users/4622463/angussidney", original_msg=msg) == \
-            "User is not blacklisted (`4622463` on `stackoverflow.com`)."
+            "User is neither blacklisted on `stackoverflow.com` (`4622463`) nor network-wide"
         assert chatcommands.rmblu("https://stackoverflow.com/users/4622463/angussidney", original_msg=msg) == \
             "The user is not blacklisted. Perhaps they have already been removed from the blacklist. Please " \
             "see: [Blacklists, watchlists, and the user-whitelist: User-blacklist and user-whitelist]" \
@@ -608,16 +608,16 @@ def test_blacklisted_users():
 
         # Format: !!/*blu userid sitename
         assert chatcommands.isblu("4622463 stackoverflow", original_msg=msg) == \
-            "User is not blacklisted (`4622463` on `stackoverflow.com`)."
+            "User is neither blacklisted on `stackoverflow.com` (`4622463`) nor network-wide"
         assert chatcommands.addblu("4622463 stackoverflow", original_msg=msg) == \
             "User blacklisted (`4622463` on `stackoverflow.com`)."
         # TODO: Add test here as well
         assert chatcommands.isblu("4622463 stackoverflow", original_msg=msg) == \
-            "User is blacklisted (`4622463` on `stackoverflow.com`)."
+            "User is blacklisted on `stackoverflow.com` (`4622463`), but not network-wide"
         assert chatcommands.rmblu("4622463 stackoverflow", original_msg=msg) == \
             "The user has been removed from the user-blacklist (`4622463` on `stackoverflow.com`)."
         assert chatcommands.isblu("4622463 stackoverflow", original_msg=msg) == \
-            "User is not blacklisted (`4622463` on `stackoverflow.com`)."
+            "User is neither blacklisted on `stackoverflow.com` (`4622463`) nor network-wide"
         assert chatcommands.rmblu("4622463 stackoverflow", original_msg=msg) == \
             "The user is not blacklisted. Perhaps they have already been removed from the blacklist. Please " \
             "see: [Blacklists, watchlists, and the user-whitelist: User-blacklist and user-whitelist]" \