diff --git a/yama/src/pile.rs b/yama/src/pile.rs
index 8ae7639..11c7074 100644
--- a/yama/src/pile.rs
+++ b/yama/src/pile.rs
@@ -26,6 +26,7 @@ use std::collections::HashSet;
 use std::fmt::Debug;
 use std::sync::{Arc, Condvar, Mutex};
 
+pub mod access_guard;
 pub mod compression;
 pub mod encryption;
 pub mod integrity;
diff --git a/yama/src/pile/access_guard.rs b/yama/src/pile/access_guard.rs
new file mode 100644
index 0000000..723a126
--- /dev/null
+++ b/yama/src/pile/access_guard.rs
@@ -0,0 +1,126 @@
+use crate::chunking::calculate_chunkid;
+use crate::definitions::ChunkId;
+use crate::pile::{
+    ControllerMessage, Keyspace, PipelineDescription, RawPile, StoragePipelineSettings,
+};
+use anyhow::{anyhow, bail};
+use crossbeam_channel::{Receiver, Sender};
+use derivative::Derivative;
+use std::sync::Arc;
+use std::thread;
+
+/// PileGuard is a wrapper around a pile that prevents data exfiltration and malicious corruption.
+/// It's basically a firewall for a Pile?
+/// Preventing malicious corruption requires the chunks to be unprocessed. This way, their ID can be
+/// checked by this module.
+#[derive(Debug, Derivative)]
+#[derivative(Clone(bound = ""))]
+// we need to use derivative's Clone impl because Arc<R> causes R to have a bound on Clone
+// even though that's not needed. https://github.com/rust-lang/rust/issues/26925
+pub struct PileGuard<R: RawPile> {
+    underlying: Arc<R>,
+    /// Whether to verify chunk IDs to prevent malicious corruption
+    verify_chunk_ids: bool,
+}
+
+fn pipeline(
+    subsequent_pipeline: Sender<(ChunkId, Vec<u8>)>,
+    input: Receiver<(ChunkId, Vec<u8>)>,
+) -> anyhow::Result<()> {
+    while let Ok((claimed_chunk_id, chunk)) = input.recv() {
+        let actual_chunk_id = calculate_chunkid(&chunk);
+        if actual_chunk_id != claimed_chunk_id {
+            bail!("CHUNK ID MISMATCH — is this forgery? (malicious storage process?) claimed{:?} actually{:?}", claimed_chunk_id, actual_chunk_id);
+        }
+        subsequent_pipeline
+            .send((claimed_chunk_id, chunk))
+            .map_err(|_| anyhow!("Subsequent step closed"))?;
+    }
+    Ok(())
+}
+
+impl<R: RawPile> PileGuard<R> {}
+
+impl<R: RawPile> RawPile for PileGuard<R> {
+    fn exists(&self, kind: Keyspace, key: &[u8]) -> anyhow::Result<bool> {
+        match kind {
+            Keyspace::Chunk => self.underlying.exists(kind, key),
+            Keyspace::ChunkHash => {
+                bail!("Access denied");
+            }
+            Keyspace::Pointer => {
+                bail!("Access denied");
+            }
+        }
+    }
+
+    fn read(&self, _kind: Keyspace, _key: &[u8]) -> anyhow::Result<Option<Vec<u8>>> {
+        bail!("Access denied");
+    }
+
+    fn write(&self, kind: Keyspace, _key: &[u8], _value: &[u8]) -> anyhow::Result<()> {
+        match kind {
+            Keyspace::Chunk => {
+                todo!()
+            }
+            Keyspace::ChunkHash => {
+                bail!("Access denied");
+            }
+            Keyspace::Pointer => {
+                bail!("Access denied");
+            }
+        }
+    }
+
+    fn delete(&self, _kind: Keyspace, _key: &[u8]) -> anyhow::Result<()> {
+        bail!("Access denied");
+    }
+
+    fn list_keys(
+        &self,
+        _kind: Keyspace,
+    ) -> anyhow::Result<Box<dyn Iterator<Item = anyhow::Result<Vec<u8>>>>> {
+        bail!("Access denied");
+    }
+
+    fn flush(&self) -> anyhow::Result<()> {
+        self.underlying.flush()
+    }
+
+    fn check_lowlevel(&self) -> anyhow::Result<bool> {
+        self.underlying.check_lowlevel()
+    }
+
+    fn build_storage_pipeline(
+        &self,
+        settings: StoragePipelineSettings,
+        controller_send: Sender<ControllerMessage>,
+    ) -> anyhow::Result<Sender<(ChunkId, Vec<u8>)>> {
+        let subsequent_pipeline = self
+            .underlying
+            .build_storage_pipeline(settings.clone(), controller_send.clone())?;
+
+        let (input_to_this_stage, receiver) = crossbeam_channel::bounded(8);
+
+        thread::Builder::new()
+            .name("yama Aguard".to_owned())
+            .spawn(move || {
+                if let Err(err) = pipeline(subsequent_pipeline, receiver) {
+                    controller_send
+                        .send(ControllerMessage::Failure {
+                            worker_id: Arc::new(String::from("accessguard")),
+                            error_message: format!("err {:?}", err),
+                        })
+                        .expect("This is BAD: failed to send failure message to controller.");
+                }
+            })
+            .unwrap();
+
+        Ok(input_to_this_stage)
+    }
+
+    fn describe_pipeline(&self) -> anyhow::Result<Vec<PipelineDescription>> {
+        // TODO(question) Should we be described in the pipeline?
+        self.underlying.describe_pipeline()
+    }
+}