diff --git a/sas/sasjs/services/hooks/mpe_security_postedit.sas b/sas/sasjs/services/hooks/mpe_security_postedit.sas
index 7697bc4..4110c42 100644
--- a/sas/sasjs/services/hooks/mpe_security_postedit.sas
+++ b/sas/sasjs/services/hooks/mpe_security_postedit.sas
@@ -19,6 +19,11 @@
 data work.staging_ds;
   set work.staging_ds;
   LIBREF=upcase(LIBREF);
+  if LIBREF in ('WORK','CASUSER','SASUSER') then do;
+    putlog "ERR" +(-1) "OR: invalid LIBREF - " LIBREF;
+    call symputx('errval',1);
+    call symputx('errmsg',"Invalid LIBREF: "!!LIBREF);
+  end;
   DSN=upcase(DSN);
   ACCESS_LEVEL=upcase(ACCESS_LEVEL);
   if ACCESS_LEVEL not in ('EDIT','APPROVE','VIEW','SIGNOFF','AUDIT') then do;
diff --git a/sas/sasjs/services/hooks/mpe_tables_postedit.sas b/sas/sasjs/services/hooks/mpe_tables_postedit.sas
index 6a9c754..974c0bd 100644
--- a/sas/sasjs/services/hooks/mpe_tables_postedit.sas
+++ b/sas/sasjs/services/hooks/mpe_tables_postedit.sas
@@ -39,6 +39,13 @@ data work.staging_ds;
   audit_libds=upcase(audit_libds);
   rk_underlying=upcase(rk_underlying);
 
+  /* do not accept certain librefs */
+  if LIBREF in ('WORK','CASUSER','SASUSER')
+  then do;
+    call symputx('errmsg',"Invalid LIBREF: "!!LIBREF);
+    call symputx('errflag',1);
+  end;
+
   /* check for valid loadtype */
   if LOADTYPE not in ('UPDATE','TXTEMPORAL','FORMAT_CAT','BITEMPORAL','REPLACE')
   then do;
diff --git a/sas/sasjs/targets/viya/macros_viya/dc_getlibs.sas b/sas/sasjs/targets/viya/macros_viya/dc_getlibs.sas
index cfac4e6..84c6c34 100644
--- a/sas/sasjs/targets/viya/macros_viya/dc_getlibs.sas
+++ b/sas/sasjs/targets/viya/macros_viya/dc_getlibs.sas
@@ -21,7 +21,7 @@ create table &outds as
     ,engine
     ,'' as libraryid length=17
   from dictionary.libnames
-  where libname not in ('WORK','SASUSER');
+  where libname not in ('WORK','SASUSER','CASUSER');
 insert into &syslast values ("&DC_LIBREF", "&DC_LIBNAME",'','V9');
 
 %mend dc_getlibs;